A STREET drinker who sexually assaulted a "highly vulnerable" 18-year-old girl under a city centre bridge has been jailed for five years and four months.

Homeless alcoholic Gary Taylor, 54, admitted sexually assaulting the girl, who suffered from mental health problems.

Taylor, who has two previous convictions for sexually assaulting lone women on trains, will also be on extended licence for three years after he is released.

Salisbury Crown Court heard that on June 14, 2014, Taylor had approached the girl on a bench and asked for a cigarette before offering her a sip of whiskey and sexually propositioning her.

She told Taylor she did not want it to happen and it was "rank" and she felt "sick and terrified."

But Taylor persisted and shouted at her to sit down beside him on the ground.

The court then heard that Taylor took his victim to the bridge at Summerlock Approach, near LA Fitness, under which he had been sleeping rough.

There he put his hand down her trousers and sexually assaulted her.

He was initially charged with deliberately targeting the vulnerable victim, who cannot be named for legal reasons.

But despite referring to her as a "mongoloid", Taylor denied targeting her because she was mentally unwell and the prosecution accepted his basis of plea.

Defending, Chris Smyth said his client had saved the victim from having to give evidence in court by pleading guilty on the second day of his trial.

Mr Smyth argued the attack was not prolonged or forceful, but rather "fleeting and transient", which the prosecution also accepted.

The judge described Taylor as having a "very long history of offences for dishonesty", including burglary and shoplifting, but said most important were his two previous sexual offences against lone women on trains.

He said: "This is a further offence of sexual violence against a women alone."

A doctor's report found Taylor was at risk of further sexual offending if his accommodation and alcoholism problems were not addressed.

The report said he lacked victim empathy and "minimalised his past sexual offending behaviour".

When released from prison, Taylor must comply with the requirements of a sexual harm prevention order, which includes limiting his contact with women and girls.