London in the summer: drinks in the park, tourists flocking to see Big Ben, events every night to go and see. It’s the best place on Earth. Well, when you’re not commuting that is.

In a (very) unscientific experiment, SWLondoner armed itself with a thermometer, and hit some of the capital’s Tubes to see just how hot it got.

Northern

The first leg on our torturous train journey is the Northern line, from South Wimbledon. By the time we reach Clapham Common, the top temperature has reached 32.1c and I already feel like a bottle of curdling milk. Foolishly I think that it can’t get any worse – but little was I to know the Egyptian style heat that would later hit me.

Bakerloo

A woman with impressively blue eyeshadow is fanning herself with copies of the Metro. A balding man opposite me is wiping his forehead with a packet of tissues. They’ve both got the right idea: on the oldest line on the network, our heat-reading gizmo says the max temperature is a baking 33.3c.

Central line

Surely it can’t get much hotter? But the Central Line is notoriously stuffy. It’s like being in a coffin with a hairdryer that won’t turn off. I get on at Oxford Circus, and unluckily a swarm of schoolchildren climb in after me. We’re more densely packed than a clown car, and it shows. At its worst, the thermometer hit a whopping 34.8c — nearly five degrees higher than the legal limit for transporting cattle.

Piccadilly

Several commuters I spoke to bet on the Piccadilly Line being the hottest (after looking at me as if I was mad for riding a bunch of hot Tubes all day). But that’s not what the science says. When riding from Oxford Circus to Holborn, the thermometer tells me the max temperature is apparently 32.4c. Only 32.4c? It’s practically chilly.

Victoria Line

I change at King’s Cross, and tourists clamour around with bulky suitcases. The hot air is coating me like a thick fleece. Thankfully, however, breeze floats down from the open windows at each end of the carriage. At this point, it feels like seeing a pool of water in the middle of a desert. However, it doesn’t make any difference to our thermometer, which records a max reading of 32.4c.

Passengers’ verdicts

After experiencing the searing heat of a London commute for ourselves, we asked travellers if they were happy with the temperatures on the Tube.

“It’s far too hot, especially because they’re so crowded,” said Sue, who was travelling to South Wimbledon on the Northern Line. “Especially this morning and in the evenings so they should be doing something about it.”

“Why go to a sauna when you could just get on the Tube?”, said Paul, who regularly uses the Northern Line.

“I think by now after all the decades it’s been running, they would have thought of air conditioning. Call me old-fashioned!”

Pauline, who was getting off at the end of the Northern line at Morden, added: “In the middle of London, it was packed. It was stifling.”

In a statement, TFL said: “We completely understand that travelling can be uncomfortable during periods of hot weather and are investing millions of pounds to make the Tube and buses cooler for customers.

“We are constantly working on new ways to keep the temperature down on the Tube and have doubled the number of fans on the network since 2012 as well as installing chiller units to pump in cold air.

“There are also 192 air-conditioned trains serving 40 per cent of the network. All of our buses have opening windows and all new double-deck buses use air cooling systems.

“During this hot weather we advise customers to ensure they have water with them when they travel in order to stay hydrated.”