In the changing rooms backstage at Proud Cabaret in London, half a dozen performers are crammed together preparing themselves for the evening’s shows. As one liberally applies eye makeup, another fills the air with a cloud of hairspray. There are nipple tassels, high heels, leather and wigs. It’s 8pm and the night is about to begin.

“There’s always a buzzing atmosphere while everyone prepares for the doors to open,” says Fiona Jay-Brown, one half of the acrobatic duo Deux Ailes.

“There are a lot of performers so it does get very busy backstage but we all do our best to get the show on the road. There’s rarely a backstage panic. Whether it’s missing tit-tape or hairspray running out, we all help each other out.”

• Performers including Fiona and Cory of Deux Ailes (above), Abi Collins, Didi Derriere and Dave the Bear preparing for their shows at Proud Cabaret. Main image of Chastity Belt, the compere. All photos by Sean Smith for the Guardian
  

• Fire officers Eddie Brennan and Paul Chambers patrolling the Palace of Westminster

Over at the Houses of Parliament, the scene is quiet and the politicians are long gone. Fire officers Eddie Brennan and Paul Chambers sweep through the House of Lords, past the empty benches, along more than three miles of corridors and down into the bowels of the famous structure, patrolling for potential fire hazards.

“It’s a world heritage-listed building and I don’t want to go down as the next Guy Fawkes!” quips Brennan.

Drawn from the London Fire Brigade, Brennan and his colleagues oversee numerous government buildings in the area. This past year they have investigated more than 200 alarms and reports of fire “but, touch wood, we haven’t had to fully evacuate the palace in the four years I’ve been working here,” he says.

Much of the current palace was built following the devastating fire of 1834. The architect, Charles Barry, used brick, stone and iron to try to minimise the risks of another catastrophe but in the interiors he and Augustus Pugin used vast quantities of highly flammable materials.

That said, Brennan notes that people present the greatest risk. “You’ve got people laying data cables next to old plumbing and it’s all out of sight, out of mind; you find people propping the fire doors open and forgetting to switch off stoves and heaters and lamps. Even after the latest round of modifications, the palace will always be vulnerable to fire.”

Bridge operators

• (Above) Tower Bridge at night as a vessel passes beneath; (below) a cleaner at work on the overhead walkway

Further down the river, another London landmark, Tower Bridge, is also staffed at night. The bridge is raised around 850 times a year for registered vessels with a mast or superstructure of nine metres or more.

Tower Bridge was the largest and most sophisticated bascule bridge ever built when it was finished in 1894. The lifting mechanism was originally operated using steam to power the enormous pumping engines; these days the hydraulics are driven by oil and electricity while the upper walkway – now a function space with a glass floor offering views directly over the Thames – is lit in vivid pink.

• Transport for London road workers close off the Upper Thames Street tunnel for scheduled maintenance
  

With the roads relatively free of congestion, Transport for London begins night maintenance work at the Upper Thames Street tunnel. Opened in 1970, approximately 40,000 vehicles and 4,000 cyclists travel through the half-mile long tunnel every day.

In 2011 a new linear LED lighting system was installed which has cut CO₂ emissions by more than 60%, saving an estimated 163 tonnes each year.

“We have only one opportunity every three months to close the tunnel and carry out all repairs, maintenance and cleaning for the next three,” says Stewart Wilson, Asset Operations Manager. “You really feel the pressure when you have a dozen jobs that all need to be carried out at once, before the tunnel reopens.”

Homeless shelter

• Ken, aged 71, resting in bed at The Connection at St Martin’s

Westminster has become a European hotspot for homelessness, with more and more people moving to the heart of London in search of hope, opportunity and support. By nightfall, not all have managed to get a roof over their heads.

The Connection at St Martin’s, next to Trafalgar Square, provides help for approximately 4,500 people a year; its night centre accommodates up to 45 people every night – or more during severe weather – on a short-stay basis.

“Most of our clients have complex issues so our approach is to help them deal with trauma and help them to gain independence and get their confidence back,” says The Connection’s night centre manager, Paul Symonds.

“They’re really relieved to get indoors at night, to have a nutritious hot meal and to get their heads down. It’s like a pool of tranquility while you’re surrounded by the bright lights and madness of central London.”

Symonds adds: “You meet the most interesting characters you could ever hope to meet – that’s the joy of the job. I’ve always felt it a privilege really.

“We do have our challenging moments with people dealing with addiction and mental health, but generally it’s very fulfilling.”

• Paul Symonds, the night centre manager, right, walks past Eugene Frazer, one of the residents, from West Ham.

“London can be rough when you’re on the streets. I’ve had some good times, I’ve had some bad times,” says Ken, one of the residents.

“You’ve got to understand that to get into The Connection you’ve got to spend at least four nights on the street. They’ve got to see you sleeping out. There are people who’ve been out a lot longer than that, though. At least here you’ve got a bunk and the staff are quite helpful.”

• New Spitalfields Market at night, including Afghan traders, market constable Clive Thompson with his speed camera, and Dino’s cafe.

While London sleeps, Spitalfields night market comes alive with traders buying and selling goods. Around 750,000 tonnes of produce passes through the market each year and is shifted by 233 forklifts and about 2,000 employees.

The market has been on its present 32-acre site near Hackney Wick since 1992 though its royal charter dates back to 1682 when Charles II granted permission for a twice-weekly market for flesh, fowl and roots.

Peter Durber began trading at the market in 1983. “It’s still busy and bustling but it’s evolved to be a very different market over the years,” he says. “It was predominantly white trade with Jewish influence but now there’s a very large ethnic influence which has kept it alive and reflects the diversity of London.”

Durber works 12 hours, six nights a week, starting at 3am. “Any sane person would look at the hours we work and think we’re all crazy,” he says. “It’s a bit of a beast but I enjoy what I do and when you have a buzz and you enjoy what you do, the time goes very quickly.”