A persistent sex offender found guilty of standing naked on the top deck of a bus while performing a sex act has lost his appeal against the conviction.

Raymond Stevenson, 68, of Glamis Road, Bognor, was convicted by Worthing magistrates last July, of engaging in sexual activity in front of a child.

He was also convicted of indecent exposure for performing a sex act in front of motorists while leaning on a tree and making grunting noises.

Both incidents were committed while he was on bail for another offence of indecent exposure, heard by Bradford Crown Court.

His appeal against those convictions was heard by Judge William Wood and two magistrates at Chichester Crown Court on Friday.

Nicholas Hall, prosecuting, told the court that on June 7, 2006, two 12-year-old girls saw a naked man on the top deck of a bus in Worthing Road, Littlehampton.

The court was shown 15 minutes of CCTV footage from the 700 Stagecoach bus.

It showed Stevenson undressing and waving at people from the top deck of the bus while touching himself.

Stevenson claimed the man in the footage was not him and said that an injury to his leg meant he could not get to the top deck.

Medical records were produced relating to his mobility problems but no evidence was found that he was incapable of going up the bus stairs.

The second charge, of indecent exposure, relates to an incident in which Stevenson was seen performing a sex act next to a tree by a woman, her 15-year-old daughter and her daughter's friend who were passing in a car on June 14, 2006.

Joanna Paulsen told the court he was making animal-like grunting noises while touching himself in view of motorists queuing down High Street.

She picked Stevenson out from a video identity parade.

Bathsheba Cassel, defending, claimed the identification evidence was "weak" as Mrs Paulsen said she was only 99 per cent sure Stevenson was the man she saw and the two girls on the bus did not pick her client out in an identification parade.

The court heard Stevenson had 35 sexual offences against children, mainly of indecent exposure and engaging in sexual activity in front of girls, going back as far as 1963.

Judge Wood told Stevenson there was a "significant risk" he would commit more offences that could cause "serious harm to the public" and sentenced him to four years in prison.

He will serve at least two years before he is considered for parole.