By Nick Dermody BBC News Online Wales

Signed pants: Rhys Ifans with his gift to friend Paul Durden

He shot to fame as the slobbish Y-fronts wearing Spike in Notting Hill.

Now a signed - but unwashed - pair of Rhys Ifans' real-life underpants are set to become someone's ideal Valentine's gift.

And it is all in the best possible taste - at least, it is all in a good cause.

For a music charity in Swansea, south Wales, is to auction a pair of undies which the Ruthin-born actor threw at a pal during a camping trip for a laugh.

The story goes that Ifans had arranged to meet a writer friend from Swansea, Paul Durden, in California's Death Valley.

The next minute he took his underpants off and flung them at me and said 'Here, you can have these!' Paul Durden

The star had just finished filming Little Nicky in Hollywood with Harvey Keitel and had to catch a taxi into the desert to keep the arrangement.

He arrived with a bag of clothes but had to get changed in front of the campfire, where the pair were relaxing with a drink or two.

Durden co-wrote Twin Town, the 1997 British cars'n'crime caper which helped set the Welsh-speaking star on the road to fame.

He said: "We were sitting round a campfire on these bales of straw having a laugh.

"He had this expensive suit on but it took it off and flung it in the desert.

"The next minute he took his underpants off and flung them at me and said 'Here, you can have these!'.

"I said I didn't want them unless he signed them. So he did."

After snapping his friend with the autographed underpants, Durden put them - still unwashed - into a frame at his home in Swansea.

Paul Durden shows how the pants have been looked after

But he recently donated them to Tunetown, a not-for-profit body promoting live music in Wales' second city.

The pants are to be the star attraction at an auction the group is holding during its winter musical festival in the city over Valentine's weekend in aid of local musicians.

Tunetown's Events & New Projects Manager, Mallika Tucker said: "When Rhys gave the underpants to Paul, it was a bit of joke.

"I'm not sure what we're going to get for them, but it was very generous of Paul to give them to us."

It is thought someone has already offered Tunetown �300 to take the pants out of the 15 February auction.

Rhys Ifans was unavailable for comment.