Another hard day's night: Amy Winehouse out until 5am with a mystery white powder up her nose

The Rehab star, whose behavior has become increasingly troubling in recent times, played a secret gig at the Jazz After Dark club in Greek Street.

While she was meant to have been on tour playing to thousands at venues such as the Cardiff International Arena, she unexpectedly took to the stage for an impromptu performance at the small venue.

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An onlooker said: "She seemed to be having trouble working out the music. She was going back and forth, sorting out the arrangements before singing for about 15 minutes."

She then went to Balans restaurant in Old Compton Street, where she stayed until the early morning.

Wearing the same clothes from a day earlier, she again stopped off at a local store for a quick sugar fix, but that's were the sweetness ended - as she emerged, she spat at a waiting pack of photographers and fans.

A day earlier, a distraught Amy visited her husband Blake Fielder-Civil in London's Pentonville Prison.

She spent just 30 minutes in the facility, and was in a flood of tears as she arrived home and was forced to crawl under the gate of her home after losing her keys.

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It's been a chaotic month for the star - this week alone she was spotted making a 4.15am visit to a 24 hour store in Bow to pick up a giant box of ice pops.

Celebrity friend Sadie Frost was spotted arriving at her sometime residence in Bow at 6am after a distress call from the troubled star, and 24 hours earlier musician Pete Doherty also paid an early morning visit to her home.

On Sunday, a barefoot Amy was seen outside her home in just jeans and a bra.

Last week her UK tour was cancelled after a series of shambolic performances in which she slurred incoherently and stumbled round the stage.

Her spokesperson told an American magazine: "In light of recent reports, it's easy to make false assumptions, but she's getting better and she needs the space to do that."