Pet Shop Boys bring a pop masterclass to Hyde Park

"He smiled!" shouted a member of the audience in astonishment, as the Pet Shop Boys headlined London's Hyde Park.

And he was right: Chris Lowe, the band's inscrutable keyboard player, was sporting a big old grin as he bashed out the bassline to West End Girls.

He was apparently taken aback by the crowd's reception to their set, part of a day-long event held by BBC Radio 2.

"This feels so good," beamed frontman Neil Tennant from the stage. "It's fantastic to be here".

The synthpop duo, who rewrote the rules of pop in the 80s and 90s, had seemingly placed great importance on this gig, even tweaking their standard setlist to "put more hits in", Tennant told Radio 2 beforehand.

"It's quite exciting doing an hour-long set with more hits - but I think it's a set you want the audience to feel energised by."

• Radio 2 In Hyde Park - full coverage

The 40,000-strong crowd returned the generosity by joining in with classics like Suburbia, It's A Sin and Left To My Own Devices.

Never natural showmen, the duo provided visual spectacle via a large troupe of dancers, who energised Vocal with a spectacularly kinetic push-pull routine, and provided dashes of colour in their inflatable balloon costumes during the encore.

There were a few surprise guests for good measure - Years & Years' Olly Alexander duetting on the band's new single Dreamland, and Beverley Knight stunningly recreating Dusty Springfield's vocals on What Have I Done To Deserve This.

"OK, we'll do another old song," announced Tenant towards the end of the set. "But which old song? There are so many to choose from."

He teased the audience with fragments of Opportunities and Rent before the unmistakable synth riff for Go West chimed out - prompting another mass singalong, with some fans even donning the video's unforgettable conical hats.

The set ended with a snatch of 2016's The Pop Kids, a song that acts as a potted history of the band: "We were young but we imagined we were so sophisticated / Telling everyone we knew that rock was overrated."

With rock all but edged out of the charts, and artists like Charli XCX, Billie Eilish, and Years & Years building on the Pet Shop Boys' pop template, it's no surprise Chris Lowe was smiling: The gig felt like a lap of honour and a pop masterclass rolled into one.

Setlist

• Suburbia

• Burn

• Se a vida é (That's the Way Life Is)

• West End Girls

• Dreamland (with Olly Alexander)

• Vocal

• Heart

• It's A Sin

• Left to My Own Devices

• Go West

• Domino Dancing

• What Have I Done to Deserve This? (with Beverley Knight)

• Always On My Mind

• The Pop Kids

The band's set came at the end of Radio 2's Festival In A Day, where the bill also included Simply Red, Clean Bandit and Status Quo - who performed with an empty microphone stand on the stage, in honour of guitarist Rick Parfitt, who died in 2016.

Playing the support slot, Westlife drew the biggest crowd of the day for a vocally-impressive set of torch ballads, including You Lift Me Up and Flying Without Wings.

Soul star Emeli Sande, however, had to pull out of the event, saying: "I woke up this morning and my voice just wasn't there."

Here are some of the other moments worth noting:

Bananarama's lunchtime carnage

At a conservative estimate, more than 2,500 picnics were trampled into the ground as fans jumped around to Bananarama's glossy 80s pop hits: Venus, I Heard A Rumour, Love In The First Degree... The list goes on.

Speaking backstage, Sarah and Keren revealed that the last time they'd been in Hyde Park it was as fans, watching Barbra Streisand's comeback show earlier this summer.

"Actually, the first song we ever recorded was Evergreen by Barbara Streisand, on a cassette player when we were at school," Keren recalled.

Sadly, though, this pivotal moment in pop history has been lost in the mists of time.

"I've got loads of old cassettes but my brother tended to record over most of them. Bruno Brookes doing the Top 40 and that sort of thing," said Keren.

So how about recreating the cover for their next album?

"A disco version?" asks the singer. "I've just tried to imagine it in my head and... maybe not."

Francis Rossi had a gruelling training regime

Status Quo were one of the day's biggest hits - with hundreds of fans beerily recreating the hands-on-hips swivel dance for Down Down; followed by a rousing singalong to Rockin' All Over The World.

Frontman Francis Rossi seemed decades younger than his 70 years as he strutted around the stage - but that sort of athleticism doesn't come easy.

"I like to be match fit, so I had to swim double this morning to try to get myself ready," he said in his dressing room, as he limbered up his fingers on a spring-loaded grip strengthener.

"I ate at 11:30 this morning because I like to leave six hours between a meal and a show; and I do a few crunches, because that helps pop the chest and the diaphragm, for some reason."

Who said rock stars have an easy life?

Kelsea Ballerini premiered a brand new song

US country star Kelsea Ballerini, who's in the middle of recording her third album, popped across the Atlantic to play her new single, Homecoming Queen, for only the second time.

So was she nervous about playing untested material to 40,000 people? Not especially.

"I think this is probably an audience that I'll have to introduce myself to, anyway," she said modestly before the show.

"I'm prepared for none of them to know any of my songs - so it takes the pressure off of the one actual new song when all of them are seemingly new."

Clean Bandit have been working in China

Fresh from the success of composing Shawn Mendes and Camila Cabello's Senorita, Clean Bandit have been off to China, where they've been writing with two up-and-coming stars Henry Lau, and Tia Ray.

Travelling to Shanghai was a bit of an eye-opener for the band.

"We were really shocked at the studios we got taken to out there," said Jack Patterson. "They were phenomenal, you don't see new studios being built like that anywhere else in the world. It's a different level of investment in the music industry."

The band did encounter a few difficulties, though, with messaging services like WhatsApp banned in China.

"We were like, 'Why isn't anyone replying? Do they hate us?'" said cellist Grace Chatto.

"In the end, we had to use a special app."

Meanwhile, the band revealed that work had started on their third album, which could herald a change of direction.

"There are quite a few songs that we're working on finishing now that are more towards a hip-hop tempo and style," said Grace.

"That's kind of solidifying as a plan over the last couple of weeks."