The history student son of rock star David Gilmour was intoxicated and did not realise he was swinging from the Cenotaph during university fees protests in London, the Court of Appeal heard today.
Charlie Gilmour, who was studying at Cambridge University, was "aware there was a Cenotaph" and aware of "its significance", but did not realise the "monument from which he was swinging was a war memorial - let alone the Cenotaph", three judges were told.
The comments were made by a QC representing Gilmour, of Billingshurst, West Sussex, as he urged the judges to reduce the 16-month sentence imposed on the 21-year-old in July after he went on a drink- and drug-fuelled rampage during protests in December 2010.
David Spens told Lord Justice Hughes, Mr Justice Cranston and Mr Justice Hickinbottom Gilmour had been "brought up in the country" and lived "without a television for 10 years", and "it was not actually as surprising as might have been thought".
Gilmour had admitted violent disorder after joining thousands demonstrating in London's Trafalgar Square and Parliament Square.
He was seen hanging from a Union flag on the Cenotaph and leaping on to the bonnet of a Jaguar car that formed part of a royal convoy.
Gilmour was found by a judge at Kingston-upon-Thames Crown Court to have thrown a rubbish bin at the vehicle, a finding under challenge as part of the appeal proceedings.
He also kicked at the window of Topshop's flagship store on Oxford Street and ended up in possession of the leg of a mannequin.
The crown court judge had accepted that the antics at the Cenotaph did not form part of the violent disorder, but described it as "outrageous and deeply offensive behaviour".
The student was not present for today's hearing, which was attended by Pink Floyd guitarist Gilmour.
Mr Spens said his client was "keen" to learn the result of his case because then he would know whether there was any prospect of being able to continue his studies.
He told the judges Gilmour's personal mitigation was both "impressive and substantial".
The crown court heard that Gilmour had turned to drink and drugs after being rejected by his biological father, the writer Heathcote Williams, and had taken LSD and Valium in the hours leading up to the violence.
Mr Spens pointed out to the appeal judges today that he had "successfully reformed and rehabilitated himself" and, in particular, had addressed the "underlying drug and alcohol problems".
The QC said: "My submission is that this sentence was unduly harsh, unnecessarily so."
A "considerably" shorter sentence could have been passed: "In other words, a short, sharp shock, sufficient to punish him and at the same time to send out a message loud and clear to others who might be tempted to act as he did."
Gilmour's "substantial potential" was being "wasted while he spends too long in prison".
The judges reserved their decision to a date to be fixed, but it is possible a ruling will be given next week.