A teenage prisoner who sneaked an amorous liaison with her boyfriend would be considered lucky by many UK inmates.

Donna Stokes, 19, is pregnant, her boyfriend Paul Rosser, 24, is a father-to-be and a security guard at Swansea Prison is in trouble.

The couple were both in custody. But two minutes alone was all it took.

It was a rare opportunity for prison love. Not for British lags is the rocking caravan of US jails, or even the special cells, showers and towels of Spanish ones.

The British penal system, unlike that of the US, Canada and most of Europe, makes no provision whatsoever for conjugal visits.

Even the Maze prison in Belfast - a subject of tabloid hysteria over its televisions, wifely visits and other benefits in the past - has never had a policy of allowing inmates to have sex.

Throughout the UK, the prisoners who must behave most monastically are those categorised as most dangerous - category A and B prisoners and their equivalent.

They have absolutely no chance of an amorous encounter with anyone on the outside, as they are held in high security prisons and all visits to the prison are "closed" - ie, touching is not allowed.

The only hope for these inmates is to behave so well that they become reclassed as category C and D or their equivalent.

These categories are judged unlikely to escape, are housed in open or semi-open prisons, and are allowed occasional "home leave".

A Prison Service spokesman described the purpose of home leave as a way of "maintaining family ties", rather than a "conjugal visit" as such.

Depending on the individual establishment, a typical C or D prisoner would be allowed home on Friday night to Sunday night, about once every six to eight weeks, towards the end of their sentence.

In Northern Ireland, the home leave provision is more generous, but in Scotland, they must have served at least six months or a third of their sentence, whichever is the longest, to be eligible.

Such prisoners may also have "open visits", where families and friends of prisoners can sit with them. However, this takes place in a large, guarded communal room - not exactly a traditionally romantic setting.

Campaigners such as the Federation of Prisoners' Families Support Groups say the right to have sex should be enshrined by law.

But Mark Leech, editor of the Prisons Handbook and chief executive of ex-offenders association Unlock, says campaigners should be asking for more frequent trips home instead.

"I don't like the idea of a dirty weekend in a dirty caravan with staff peering in through the windows," he said. "It demeans the relationship".

He said "trusted weekends" should be used as an incentive for good behaviour right from the start of the sentence.

"Ask any prisoner what the biggest incentive to good behaviour is, and they'll say sex and freedom - in that order," he said.

A recent survey of Scottish inmates indicated that many prisoners agreed that conjugal visits were not a high priority.

Only 4% ranked conjugal visits top priority - way behind better food, a rise in prison wages and a TV set in every cell.

There have been other occasions where the rules have not deterred amorous activity, however.

Several years ago in Cardiff Prison, changes in the lay-out of the visitors' room led to a markedly more friendly atmosphere.

This resulted in a notice being put up, warning: "Keep your hands to yourself and your underpants on. Don't think sex till your visitors have gone."