David Gilmour's son's incarceration was ''deeply depressing''.

The Pink Floyd legend - who has eight children from two marriages - watched his second-born son Charlie Gilmour sentenced 16 months in prison after he was pictured swinging from a Union Jack flag on a prominent London war memorial during a student protest.

He revealed: ''Whether they deserve to be there or not, seeing your child in a prison grey tracksuit is not something I would recommend to any parent. It was a deeply depressing experience.''

But Charlie, now 29, hid the stark reality of prison life from his parents.

David, 69, said: ''While Charlie was there he did his best to shield us from the grim reality of the situation. But the sad truth is that for many people prison can be a damaging and dehumanising experience.''

But now the 'Shine on You Crazy Diamond' singer has leant his support to Liberty Choir, an organisation that's been giving prisoners a chance to perform in a singing group and which Charlie - after joining the group inside - asked his Dad to help.

He told The Independent: ''Wandsworth Prison is not a place I ever thought I would willingly return to ... Charlie had gone in with two guys who had been in the Liberty Choir at Wandsworth and were now members and supporters. He is still in touch with one of them, and he has maintained friendships with a lot of the people he was in prison with.

''It was our son, Charlie, who persuaded us that it would be really worthwhile.''