Blue star Lee Ryan has pleaded guilty to failing to provide a specimen and to criminal damage.
He was supported by his fellow band members at Ealing Magistrates' Court in west London.
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The station, which saw 44m people commuters use it in 2016/2017, will be transformed into a dining room complete with Christmas decorations.
Part of the monster fatberg will go on display in the Museum of London, while the rest of it will be converted into biodiesel.
Major engineering projects at key London stations mean hundreds of trains will be cancelled or diverted.