Kashif Ahmed pointed to a hole in the middle of the mosque's carpet where the smoke grenade landed. On 22 May this year Geoffrey Ryan kicked open the front door of the Al Falah mosque in Braintree, Essex, tossed the incendiary device inside, and brandishing two kitchen knives threatened to kill worshippers.

Five hours earlier, Drummer Lee Rigby had been murdered on the streets of Woolwich, south-east London. Muslim convert Michael Adebolajo has been charged with the killing.

The mood among many Muslim communities in the aftermath of Woolwich remains fearful. In the months since then, Braintree's only mosque has been strikingly modified. The front door is now protected by a security code, CCTV cameras monitor the entrance and police patrols frequently pass by.

Ahmed, who lives in nearby Chelmsford, believes community relations in Braintree have broadly improved since the attacks, citing gestures of support from local church groups, businesses and schools.

Yet 100m away, along South Street, two men outside the Wagon and Horses articulate a different sentiment. They are firmly opposed to the spread of sharia law. In fact, it is not something Ahmed endorses, either.

"We don't go to an Islamic country and want different laws," said one.

His friend nodded, adding: "When in Rome, do as the Romans do."

Although they acknowledge that the town's Muslim community does not cause "aggro", they admit to being relieved that Braintree's Turkish men don't wear "bedsheets".

Ahmed said that some drinkers at another pub close to the mosque can provoke tension. "On Friday and Saturday nights, you get some name-calling. They want to show off in front of their friends," he explained.

During the recent month of Ramadan, police guarded the mosque every night for two or three hours to ensure that late-night drinkers could not cause trouble. "When people are drunk, everybody has a problem. Anybody who looks different – for example, if they have a funny haircut – can get targeted," said Ahmed.

Such behaviour can make life uncomfortable for the town's modest Muslim population.

Ahmed's mosque, which opened in 2002, draws 110 families from the town's 42,000 people, yet many of Braintree's eateries and taxis are run by Muslims. One driver, Mohammed, who has been working in the area for seven years, said: "You always get the odd idiot, but 99.9% of the people are fantastic and are against that type of person."

There are few apparent signs of extremism within Braintree, unlike in Chelmsford, where three weeks ago the English Defence League (EDL) marched in protest over plans to build a mosque in the city. Leaked details of apparently senior EDL figures have listed addresses in Braintree and nearby Colchester.

Last week, three figures outside a mosque in Harlow, 30 miles from Braintree, sprayed insulation foam underneath the shuttered doors of the Harlow Islamic Centre and started a fire in an apparently premeditated arson attack. More long-term analysis indicates that, in the years since September 11, around half the mosques and Muslim centres in Britain have been subjected to attacks.

Those who have inspected the site of the Harlow attack have suggested that its owners were expecting unwelcome visitors. The doors are protected by steel shutters, light sensors, CCTV and an alarm system.

However, most nearby residents describe a relaxed neighbourhood with no tangible interfaith tensions. Dog walker Philip Lennon said: "It's a very calm area, apart from some of the young kids. There has never been any trouble between different religions."

But the voice of dissent is again soon evident. Sheila, who has lived in south Harlow for 40 years, said some residents were worried about a perceived increase in the number of Muslims.

"It's getting bad, people have had enough," she said. "I remember we managed to stop it [the Islamic centre] turning into a mosque. They were going to bring the dead bodies in, despite it being next door to the school. People don't want that."

Yet the truth is that the town's Muslim population of 2,000 out of a total of 82,000 keeps a low profile.

The Islamic centre is discreetly located on the town's southern periphery, barely visible from the road. "I've been driving past it for three years and never even noticed it.

"I didn't even know we had a mosque until the house fire last year," said Angela Hudson, 38, referring to last year's fire in Harlow that killed a woman and all five of her children. Their father, Abdul Shakoor, worships at the mosque.

The police investigation into last week's attack continues, with forensic science experts examining the building and detectives sifting through CCTV footage for clues.

Local gossip suggests that the arsonists might merely have been youths from the nearby Milwards estate. One passerby said: "They'll do anything after they've had a drink."

Yet the aftermath of the Woolwich attacks has drawn attention to the fact that the far right, particularly the EDL, is behind many of the attacks, with the group recently linked to a third of cases of Islamophobic abuse online.

The revelation that Ryan – who was jailed last week for nine months for his attack on Braintree's mosque – had ties to the EDL came as little surprise. Similarly, anti-racism campaigners expect those who attacked Harlow's mosque to be revealed as extremists.