The basement of Debenhams in Clapham Junction was pitch black – but the department store was not empty. As soon as the shopfront was smashed at the height of the riots on the evening of 8 August, the looters began pouring in.

It was the noise which many rioters remembered. Yelps of excitement could be heard above the sounds of clothes rails crashing over, tills being smashed and a wailing alarm as the crowd ran up and down escalators, grabbing what they could.

"It was like Christmas; it was so weird," said one, a 16-year-old girl from nearby Lavender Hill. "Snatch and grab, get anything you want, anything you ever desired," said another, a 19-year-old man from Battersea.

The looting of Debenhams was just one attack, in one shop, among thousands of incidents during the riots. But the picture of the few hours during which it was ransacked, built up through a series of interviews for the Guardian and London School of Economics research project, captures the wave of excitement that spread across England as people felt they could "get stuff for free".

"It was black, yeah, like all you could hear was 'whoo, whoo, whoo, whoo, whoo' alarm flashing off," said one looter from Lambeth, who had been told by a friend via the BlackBerry Messenger instant message service that it was "going off" in Clapham Junction and no police were present.

"It's crazy. Crazy. I see glass everywhere. There was clothes all over the floor. Boxes. There was every kind of thing on the floor. I couldn't believe it. There was plastic bags, normal bags, aftershave, perfume, knickers, bras, boxer shorts, vests. Everything was on the floor."

Other voices paint a surreal picture of an evening when normal rules no longer applied. "People were picking up things like it was in their homes and it was theirs already. It was weird because it was like: 'Is this a trick?' You want to do it but you don't, because you don't know," said the 16-year-old girl from Lavender Hill. "Downstairs it was pitch black … People running across from one place to another. It was weird. Everyone just looked really greedy."

Looters cleared the shop in hours. Asked about the most remarkable thing he had seen during the riots, a 20-year-old from Wandsworth said: "Debenhams was empty. There was a few women, yeah, just having a little shop, but it was empty. Debenhams was empty."

About 2,500 shops and businesses are estimated to have been looted during the riots across England this summer. Looting was – according to the breakdown of criminal charges – the most common type of unlawful activity.

Across England, looters appeared attracted to fashion retailers and stores containing high-value goods – the electrical store Currys was a common target, as were jewellery shops. But looters also spoke about how they broke into cheap supermarkets, such as Lidl and Aldi.

The cost in insurance claims to the London economy alone was estimated to be up to £300m. But why did the looting happen? Why did so many people, some of whom had never been in trouble with the police before, enter shops that had been broken into and help themselves to what they wanted?

The hundreds of looters interviewed as part of the Reading the Riots study reveal complex and varied motivations. It was down to simple greed, say some participants. One 19-year-old from Hackney, who looted in Wood Green on the first night of the disturbances, put it in stark terms: "The rioting, I was angry. The looting, I was excited. Because, just money. I don't know, just money-motivated. Everything that we done just money-motivated."

Reading the Riots researchers spoke to looters who said they made thousands of pounds from selling items stolen during the riots. A 22-year-old man from Stockwell said he ended up with £2,500 after splitting the proceeds from electrical goods looted in Clapham Junction with five friends.

A database of riot-related court cases compiled by the Guardian as part of the research confirms that many looters were highly organised and targeted goods with maximum resale potential. An 18-year-old and two younger teenagers were jointly charged with looting £5,000 worth of electrical equipment from Currys and Comet in Greenwich, £500 worth of cigarettes and alcohol from a nearby petrol station, and with trespass and intent to steal from Halfords and PC World.

Amid the sense that the rule of law was suspended, many felt they were taking part in a free-for-all with no consequences. "It would have been like a normal shopping day … but with no staff in the shop," said an 18-year-old woman from Lambeth.

A 15-year-old girl described the scenes in Clapham Junction: "There was … people filling up their cars. People holding up shutters for people. People still smashing windows when it's dark. People running in the roads with goods filled up in their arms. People going into TK Maxx, getting suitcases and filling up suitcases."

But in many interviews those involved talked of getting their "just rewards", of reacting to a society fuelled by greed, resenting being excluded from a consumerist world and placing some of the blame on big business and advertising.

Interviewees – particularly younger looters – talked about the pressure and "hunger" for the right brand names, the right goods: iPhones, BlackBerrys, laptops, clothing made by Gucci and Ralph Lauren.

One 15-year-old girl, whose mother reported her to police, described the importance of wearing the right gear. "Yeah, in our generation it is [important]. Clothes. Having the nicest clothes … the updated things, the big tellies, the fancy phones." The girl, who is now attending a young offenders' programme and will soon begin her community service, added: "People with the Ralph, the Gucci, the Nike, the trainers, the Air Forces [Nike Air Force 1 trainers], it's all the style, just everyone wants it. If you don't have it you're just going to look like an idiot. Like, that's how we see it, you just look like an idiot. It's a fashion thing."

There was a culture of "wanting stuff", said an 18-year-old man, who said he might want to be a probation officer. "It's because … it's like, seen as if you're not wearing like, and you're poor, no one don't want to be your friend."

Some interviewees blamed corporations, advertising and the media for fuelling this acquisitional consumerism. One 26-year-old from Edmonton, who had taken to the streets after the death of Mark Duggan, said he did not loot but understood why others had. "That night those young people they had freedom, because they're pushed with certain things in their face all day. Media push, like, you know: 'Buy phones, clothes, cars, jewellery.' Like, you name it, yeah, it's pushed in their faces. They haven't got a job, they don't know how to get it, so when something's going on like that and all they do know is the streets, they're going out to get it."

A number of looters complained about large corporations. A 19-year-old man from Battersea described how he plundered shops at least 12 times, stashing the stolen goods in a hiding place. "I felt like I was like a ninja, on a mission … like I was jumping all in the shops, using front rolls, yeah, run in there get a bag out there quick, bum, bum, bum, put it in there, tie it up, put it back on my back, roll out, run to my little road that I know that no one else knows." But he only took from "major consumer brands", he insisted, "stuff that was like industries, businesses, like big businesses, like international businesses that are just raping the world anyway, that are just taking advantage of other people's labour". "So why can't we take advantage of them for this one moment?" he asked.

The same businesses were named time and again: Foot Locker, PC World, mobile phone outlets. JD Sports lost £700,000 worth of stock during the riots and was a key target, according to interviewees: the 16-year-old girl from Lavender Hill went so far as to say that, in the days following the riots, her room "looked like JD Sports". But there was little sympathy among looters. "JD is making like what – £50 off a shoe?" said a 20-year-old from Clapham.

He was among a handful of interviewees who tried to justify their actions by alleging that products sold by JD Sports were produced using child labour. JD Sports told the Guardian that the companies that produced the clothing it sold, and the firm itself in the case of its own-brand products, went to strenuous efforts to "adhere to high standards of social responsibility".

Looters found it harder to justify why they broke into small, independent retailers. These were often the easiest to break into and 213 were hit.

"We got to a Rolex shop and one person got a bin and hit the Rolex shop – tried to break in," a 16-year-old boy from Birmingham said. "But he couldn't break into the shop so he kept on trying various shops like, went to Rolex, the bank, went to every shop there." They eventually settled on a corner shop and stole cigarettes.

Shops of all types were struck during the riots, and a dizzying variety of goods taken, the interviews reveal. Interviewees described people stealing rice, pasta and nappies. One "self-employed pharmacist" (cannabis dealer) from Tulse Hill in south London recalled taking goods from the high end ("I got two plasmas. And I was satisfied") as well as the low ("[We] moved on to the next shop. Obviously, I had a couple of munchies. Obviously got some Haribos, alcohol, cigarettes").

Other looters took a similarly eclectic approach. One in London was charged with stealing two wedding dresses and a bicycle; an 18-year-old man in Manchester was charged with stealing vintage clothing and lottery tickets; another took 75 cans of Lynx deodorant and 50 Rimmel mascara sticks. One man in south London worked his way down his local high street, stealing items that might have appeared on any mundane shopping list: hair products from one shop, cigarettes from another, jeans, electrical goods.

A report from the Home Office into the crimes and arrests resulting from the riots revealed that 51% (2,584) of the crimes committed during the disorder were against commercial premises, but that figure varied throughout the country: in London 57% of the crimes committed were "acquisitive" compared with 10% in Nottingham, for example. Of the 1,385 shops hit throughout the country the most targeted were electrical stores (265), followed by clothes shops (233).

Some rioters tried to get their hands on cash: one 16-year-old girl from Wandsworth said seeing people "pulling the ATM machine out of HSBC" in Clapham Junction was her first image of the riots. Betting shops were also regularly attacked. A 23-year-old in Salford said that in Manchester pawn shops were the first target. "People like: 'I'm gonna get me telly back,'" he said.

Many of those who took part described a sense of euphoria during the looting, combined with a disbelief that they were not being stopped as police struggled to cope. "People were smiling. It was just everyone was smiling. It was literally a festival with no food, no dancing, no music, but a free shopping trip for everyone," said one 16-year-old girl from Wandsworth.

A 22-year-old woman from Stockwell said: "It was a happy atmosphere. I remember there were a lot of people laughing and giggling and just picking up whatever they liked, just taking it, running in, running back out. It was just a happy vibe."

One 18-year-old in Birmingham described picking up a bag of phones from T-Mobile in the city centre and throwing them into the air in the street.

One 22-year-old from Southwark, who stashed about 10 iPhones in his pockets and looted through the night, described the ease of breaking into a Carphone Warehouse. "We literally teared up the shutter. Like all right it was night-time now, but people in their cars are just driving by watching. Police are zupping past what we're doing and going to another emergency and it was just easy. You had ransack of the place."

But he attempted to justify what he had done. "I think, personally, western society as it is, we live in a mad, materialistic sort of society where everyone's got to have the latest iPhone, television, whatnot," he said. "I don't know, there's no jobs out there and people what, they want to feel part of, they're moving with the times I suppose, to a certain degree. And things are too expensive."

Among some interviewees – such as the 19-year-old from Battersea who felt "revolutionary … against capitalism" – there was a sense that an opportunity to change society had been lost. "They fucked up big time, the opportunists," said a 19-year-old man from Tottenham, who observed the riots but did not loot. "If they went to parliament and stood up for what they thought was correct, they could have brought down the government, man. We could have changed the whole everything, the whole government, man, but people wanted Nikes and crap on their feet."

For others, there was a sense of personal regret. A 15-year-old girl described being scared on the night the riots flared up in her area. She had not wanted to take part. "But then after it all kicked off and everyone was doing it you just joined in and it felt fine. It just felt natural, like you was just naturally shopping," she said. But subsequently she handed herself in to the police, and, asked what she thought about her actions now, she said: "I'm ashamed. To think that I went that low to go steal in these shops when they're, like, basically that's their business, that's how they're providing for their families, and we've basically ruined that and they've got to start from scratch." A 19-year-old man added that he felt like he had lived up to a stereotype. "I just think, because they're labelling young black people in that sort of way, I just think I just proved them right by doing that," he said.

The 18-year-old looter from Birmingham who threw the phones in the air argued that anyone would do something that would benefit them if they had the opportunity. "If I could get a job, I'd get a job … and I'd live life like that. If you can't get a job, you'd find any way possible to get money to live, basically. Because … money is the necessity to contribute. You need money to get anywhere."

But, in a moment of reflection, he said what he had done was still wrong. "Because you're messing up your own economy for what, for games maybe? Phones," he said. "But at the time it didn't feel wrong, you know what I mean? So, if you look back on it you're like: 'Oh, you did the wrong thing,' but you can't correct the past, can you?"