Is this Amy Winehouse snorting a 'mystery substance' while live on stage?

The troubled singer, who has previously admitted to a heroin addiction and once collapsed after a drugs overdose, seemed to take a parcel from her bra and put it up towards her nostril.

She then veiled a silk scarf in front of her face for a few moments before agitatedly rubbing her nose.

Winehouse, 24, then struggled to string a coherent sentence together as she exchanged banter with the crowd at the Brixton Academy between songs.

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The award-winning singer was pictured on stage in Blackpool earlier this week with what looked like white powder blobbed up her nose.

The London show on Thursday evening was by all accounts a memorable one.

The lyrics and her asides to the audience were littered with references to her currently incarcerated husband Blake Fielder-Civil.

The 25-year-old was remanded in custody a fortnight ago accused of perverting the course of justice and causing grievous bodily harm. Mr Fielder-Civil appeared in court in London yesterday and Winehouse was there to support him.

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The previous night appearing in a tiny, pink patterned mini-dress Winehouse dedicated a rendition of Sam Cooke's Cupid to her husband, proudly reminding the crowd it was her six-month anniversary only four days before.

When she came to her encore Valerie, the song was re-jigged in her customary style, with her singing: "I'll get you out of jail, my Blakey" in typically soulful fashion.

As she prepared to launch into Wake Up Alone, she announced: "This is my husband's favourite song, I usually sing it to him, but he's not here," much to the delight of a sympathetic crowd.

Winehouse had finally appeared on stage an hour late, flanked by a nine-piece band clad in black suits to a backdrop of a swinging 1950s jazz club.

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In contrast to recent shows, her late arrival was followed by a sensational performance which delighted the 4,000 strong crowd at her first London appearance on her sell-out tour.

Coming along to support Mrs Winehouse in the absence of Fielder-Civil was Arctic Monkeys front-man Alex Turner, singer Kelly Osbourne and Kimberley Stewart, while the singer also proudly announced that her long-suffering father had come to watch her performance.

Members of the audience were quick to praise the performance of the 24-year-old singer after a disastrous start to the tour.

"She really brought it out the bag with this performance," said 21-year-old fan Carmella Rubenchik.

"I thought with Blake's trial coming up she would be a bit wobbly. She changed a lot of the songs to mention him, but it was wonderful."

"She was fantastic, her performance was top notch and much better than we thought it might have been after what happened in Birmingham," said Shereen Parker, 25, from South London.