Britney Spears‘ mental health came under heavy scrutiny following her performance of Gimme More at the 2007 VMAs – in which the disorientated star sloppily mimed and seemed to forget the dance moves.

But an unearthed clip of the star’s dress rehearsals for the now-iconic performance shows Britney pulling off a flawless routine, in stark contrast to the shambolic performance she put in on the night – leaving fans baffled, until now.

In her explosive memoir, The Woman In Me, the star revealed she’d had an extremely awkward backstage run-in with ex Justin Timberlake before her performance, writing: ‘It had been a while since I’d seen him. Everything was going great in his world.

‘He was at the top of his game in every way, and he had a lot of swagger. I was having a panic attack. I hadn’t rehearsed enough. I hated the way I looked. I knew it was going to be bad.’

Before the run-in Spears looked polished and in great spirits in her dress rehearsals for the performance, at one point donning a large hat and jeans for one run-through – before wearing her famous sparkly lingerie with her hair in a ponytail.

Iconic: Britney Spears ‘ mental health came under heavy scrutiny following her performance of Gimme More at the 2007 VMAs (right)- but an unearthed clip of the star’s dress rehearsals (left)  for the now-iconic performance shows Britney pulling off a flawless routine

Gimme more: Before the run-in with Justin Timberlake, Spears looked polished and in great spirits in her dress rehearsals for the performance (top) compared to the performance (bottom)

Awkward: In her explosive memoir, The Woman In Me, the star revealed she’d had an extremely awkward backstage run-in with ex Justin Timberlake before her performance (pictured 2007)

Spears looked notably more energetic and happy in the dress rehearsal leading fans to comment: ‘Damn this rehearsal is better than the final performance ..she obviously show her emotion here ..look at her face she’s really into it.’

Another wrote: ‘I cannot wait to hear her story behind this performance now that she’s free to speak. Something definitely happened between the rehearsal and the actual performance

Others penned: ‘She looked much better in a ponytail and in jeans. I don’t know why they finally released her with this hairstyle and clothes. but britney is a legend icon anyway!

‘Only britney has iconic rehearsal’ and ‘The 1st rehearsals looked pretty good . Looks like performance got worsened by the time actual performance.’

After taking to the stage in nothing more than her underwear and sporting extremely visible hair extensions due to shaving her head months before – the singer’s big comeback came to a grinding halt.

The performance shocked fans and was universally panned by the public and critics.

She wrote of the moment: ‘There was a problem with my costume and with my hair extensions. I hadn’t slept the night before. I was dizzy. It was less than a year since I’d had my second baby in two years but everyone was acting like my not having six-pack abs was offensive,

‘I couldn’t believe I was going to have to go out onstage feeling the way I felt.

Britney Spears sports crop top and bikini bottoms during knife dance

Experimenting: Spears donned a large hat in one rehearsal and tied her locks back in another

Looking good: The star showed off her now-famous stage outfit as she worked her way through the routine

Different look: The star also wore jeans and a crop-top for another rehearsal

Difference: Spears looked notably more energetic and happy in the dress rehearsal leading fans to comment: ‘Damn this rehearsal is better than the final performance

Gimme More! The star belted out the track in the dress rehearsal (top)

Concern: Spears sparked huge concern with her final performance

Released October 24: Spears’ memoir, The Woman In Me, has unleashed a series  of bombshells

The way they were: When Britney began dating wholesome NSYNC star Justin Timberlake in 1999 — fans all over the world saw them as America’s golden couple (pictured in 2002)

 ‘I went out there and did the best I could at that moment in time, which — yes, granted — was far from my best at other times. I could see myself on video throughout the auditorium while I performed; it was like looking at myself in a fun-house mirror.’

Months after her VMA performance in January 2008 Spears was hospitalized at Cedars-Sinai Medical Center after police arriving at her house – after she locked herself in a bathroom with her sons and refused to turn them over to Federline – noticed she appeared to be under the influence.

Federline was given sole legal and physical custody and Spears was placed on a 5150 involuntary psychiatric hold and committed to the psychiatric ward of Ronald Reagan UCLA Medical Center.

Spears would regain visitation rights to her sons in July 2008 and began a return to the spotlight with a documentary and TV appearances.

She would share occasional snapshots of her with the boys over the years – beaming at the camera at a baseball match, celebrating birthday dinners, splashing around in a swimming pool – suggested a tender bond between mother and sons was forged.

But Federline was reportedly given 70 percent custody in 2019.

Kevin now notably has full custody over their two boys and made the decision to move the family from Los Angeles to Hawaii recently.