True Bromance: Robbie Williams and Gary Barlow relight the fire with a hug as they premiere duet Shame

Newly married Robbie Williams looked thrilled to be back in Britain and with his best buddy again Gary Barlow as the pair launched their first ever duet this morning.

They both looked toned, tanned and healthy as they posed outside Radio 1 in London, where their new single Shame had just got its first airing.

The track - which Radio 1 listeners pointed out has a very similar guitar chord sequence to the Beatles' song Blackbird - was jointly written by the reunited bandmates.

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Best friends: Gary Barlow and Robbie Williams were greeted by dozens of screaming fans when they left Radio 1 after promoting their new duet Shame

Everything changes: The former boyband buddies might have a few more grey hairs but they've rekindled their old friendship

It's the first time they've worked together in 15 years since Robbie acrimoniously left Take That.

The single, which is released on October 4, is taken from Williams' upcoming greatest hits album In And Out Of Consciousness which follows the week after.

Williams revealed today that the band would definitely tour - but the collaboration may not be permanent. The duo said the group's only firm plans are for an album and live shows.

After 18 months working, the future is uncertain and they may go their separate ways, they admitted as they appeared on BBC Radio 1 this morning to unveil the single.

The group and Williams had bickered for more than a decade after he left for a solo career. They cleared the air after more than a decade of feuding when they met up in Los Angeles around 18 months ago.

Last month they announced they had recorded an album.

Today the pair confirmed they were plotting their live show - but anything beyond that was uncertain.

Asked about the future, Barlow said: "I don't know the answer to that. We agreed when we started - it's 20 years since we began, it's our 20th year for all of us - to do a one-off album and maybe a one-off tour would be a great thing this year.

The old pals act: Robbie and Gary look overjoyed to see one another again

But I think once we've done that, Rob will go back to being Rob, we'll go back to being a four. I think it will resume to how it was."

Williams added: "The thing is, the door is open to do whatever we want. We've got 18 months planned. Whatever happens after, whatever happens after that. We haven't decided."

Barlow said of live plans: "We are talking about a tour right now, so hopefully next summer we will tour."

The pair also spoke of the night they put their differences aside to reform the hugely popular group.The five Take That members met up 18 months ago in Williams's home city of Los Angeles, California, after keeping their distance since 1995.

In their first joint interview in 15 years, Barlow admitted that he felt guilty about not looking out for Williams, who was the younger member of Take That.

'I think we had a lot of guilt, the four of us, because Rob was the youngest, the most impressionable of all of us. We always felt like we didn't look after him enough."

The pair got together for a "big chat" when Mark Owen, Jason Orange, Howard Donald and Barlow were in LA mixing The Circus album.

Williams said in an interview on Radio 1: "It is one of those situations in life that could be very explosive and could go completely wrong.

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"We had that big chat and the most amazing thing happened at the end of it. We both said sorry to each other and we both meant it and that was all we needed.

"It just lifted so much off my shoulders that I didn't know was still there."
Barlow added: "I spent the last 15 years thinking about what I was going to say."

The pair were debuting their joint single Shame on Radio 1's Chris Moyles show. The track includes an acoustic guitar part reminiscent of Sir Paul McCartney's song Blackbird, which he recorded with the Beatles.

The 36-year-old star is celebrating 20 years in the music business - as well as his marriage to sweetheart, actress Ayda Field, 31, at the beginning of this month.

Barlow, 39, and Williams got back on stage together for the first time since Take That split at last year's Children In Need.

It was then announced in June that Robbie and Gary were working on music together, before the momentous news in July that Robbie was back in Take That.

Tartan paint: Robbie unhappily stares back at Gary on his way back from the shops

The video for Shame - the lyrics to which are about the pair's formerly troubled relationship - was also unveiled for the first time this morning on YouTube.

With a tongue-in cheek nod to Brokeback Mountain, the video is set in small-town America and begins with the pair glaring at each other from across the street, before they bump into each other again in a bar and make up over a drink.

In typical man fashion, they then go on a bonding fishing trip, complete with meaningful glances on the banks of a lake, before they both strip to the waist to prepare to dive into the water.

They both scale a mountain overlooking the inviting depths - but then decide it's too steep to jump from.

The lyrics include: 'I don't recall the reasons why. I must have meant them at the time. Is this the sound of sweet surrender? I wrote a letter in my mind but the words were so unkind about a man I can't remember'.

Elsewhere, the pair sing, 'what a shame we never listen, I told you through the television', 'my tears could fill the Albert Hall,' 'words come easy when they're true' and 'with your poster 30ft high round the back of Toys R Us'.

The track has been greeted ecstatically by fans. One calling themselves Sandra May and posting on the song's official video page on YouTube said: ' Love it! Almost makes you cry with the lyrics and makes you laugh with the video.'

Set 'em up: The Take That stars prop up the bar in the video for Shame

Another going under the name 4evatakethat gushed: 'Love love love this song and video, the vid is sooo good, my heart skipped a beat when they started taking their clothes off. I was hoping they would include the best bit of Brokeback mountain, LOL. This is too good for words!'

And Bsbgirlisrael posted: 'Love the video and the song! I love it that they finally made up and that the lyrics and the video show that.'

The pair are due to debut the song live meanwhile when Robbie headlines the Help For Heroes concert at Twickenham Stadium on September 12.

The line-up also features Alexandra Burke, Enrique Iglesias, Katherine Jenkins, The Wanted, Pixie Lott, The Saturdays, James Blunt and Plan B.

Hosts included John Bishop, Kevin Bridges, Jack Dee, Jason Manford and Michael McIntyre.

Pause for thought: The pair sit on the banks of a lake and ponder the past

Tall order: The reconciled pair decide that jumping off a cliff isn't such a good idea after all

Gary and Robbie released a statement saying: 'It's great that people love Shame so much and we can't wait to perform it live for the first time at the Help For Heroes show...We hope everyone supports Help for Heroes as much as possible - it's a great bill and we are thrilled to be a part of it.'

Take That meanwhile make their comeback with Robbie back on board with the release of a new as-yet-untitled album in November.

Robbie will then join his bandmates - Barlow, Howard Donald, Jason Orange and Mark Owen - for a huge stadium tour next summer.

His return is initially said to be for one year.

Eyes have it: Shame is the first duet that Robbie and Gary have ever done together

Read more: Daily Mail