The adopted son of Pink Floyd guitarist David Gilmour is due to be sentenced today after admitting going on the rampage at a student fees protest.
Charlie Gilmour, from Billingshurst, West Sussex, was warned he could face a jail term after pleading guilty to violent disorder in May.
He was granted bail until July to give him time to complete Cambridge University exams.
Gilmour, who was accused of a string of offences over the riot on December 9, entered a non-specific guilty plea.
The 21-year-old has yet to specify whether he admits leaping on the bonnet of a car carrying royal protection officers escorting the Prince of Wales and his wife to the Royal Variety Performance.
Gilmour is accused of smashing a window at a high street store and throwing a rubbish bin at the royal convoy. The bin missed the royal couple but hit another car, it is alleged.
Gilmour had been accused of stealing a mannequin leg, but that charge was withdrawn.
He was among thousands of people who protested in Trafalgar Square and Parliament Square on December 9 and was photographed hanging from a Union flag on the Cenotaph during the march.
He issued an apology the day after the demonstrations, describing it as a "moment of idiocy", and added that he did not realise the Whitehall monument commemorated Britain's war dead.
Gilmour is due to be sentenced at Kingston Crown Court, Surrey
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