Sir Bernard, 61, was leaving Victoria station with his daughter-in-law, Christine, 31, at 4.15pm on 24 March when the man slipped through the automatic ticket barrier without inserting a ticket in the machine.
Sir Bernard told Horseferry Road magistrates' court, Westminster: 'When I got to the other side of the barrier I said to him: 'Hey, you shouldn't do that, you should pay your fare,' whereupon he said, very arrogantly and sort of intimidatingly, 'What's it got to do with you?'
'I said: 'It has got something to do with me because you are cheating. You are not paying your fare and you are cheating people who do pay their fares.' He told me to 'F. . . off.'
Sir Bernard then alerted a policeman who ushered all those involved into a British Transport Police office.
Nazir Afzal, for the prosecution at yesterday's case against Mark Coyle, 21, of Clapham Junction, south-west London, described Sir Bernard's intervention as 'public spirited'.
Coyle, who did not turn up to the hearing, had previously pleaded not guilty to using offensive behaviour and travelling on the railway without paying his fare. Ronald Moss, the magistrate, found Coyle guilty on both counts and fined him pounds 60 plus pounds 30 costs. Mr Moss thanked Sir Bernard for his intervention.
Sir Bernard was quick to play down any suggestion of heroics. 'The man didn't really offer me violence, but he was slightly threatening,' he said.
'I think more members of the public should get involved when something like this happens. It would help if criminals thought they were not going to get away with it scot-free.'