Image caption Dave Prowse played Darth Vader in the first three Star wars films

This week a Darth Vader costume dating from the era of Star Wars sequel The Empire Strikes Back (1980) is to be sold at auction at Christie's in London. We talk to actor Dave Prowse about his time as the man behind the mask.

"We were filming during the hot summer of 1976," says Dave Prowse, the man who was Darth Vader.

"The suit was made from quilted leather. I wore a t-shirt and a pair of swimming trunks underneath - and the heat would rise into the mask and mist up the eye-piece, so you couldn't see where you were going!"

Darth Vader - for those who don't know - lived a long time ago in a galaxy far, far away. For many he is the movie villain par excellence.

Prowse played the bodily form of Darth Vader in the first three Star Wars films.

But the character was voiced by American stage and screen actor James Earl Jones. (Prowse confirms the two men have never actually met, although they have spoken by phone.) "I'm a great adorer of what he did - he enhanced the part greatly with his beautiful tonal voice."

Green Cross Man

Image caption Dave Prowse is still acting in independent films

The Darth Vader costume in the Christie's auction is expected to fetch up to £230,000 ($368,000).

Prowse has seen the costume, but has not verified it as the one he wore on screen. The original Star Wars costume is in the Lucasfilm archive in the US. The last time he wore it was in the 1990s.

"They sent it over to me - with a guard - to do a Star Wars video game called Rebel Assault II. My name tag is still in the suit."

A former weightlifter and bodybuilder, Prowse played a variety of monsters on film and TV in the 60s and early 70s. When he was cast as Darth Vader he was already well known as road safety superhero the Green Cross Code Man.

As Prowse recalls, when he tried on the helmet at Elstree Studios for the first time he found he was able to move his head freely around inside it.

"I said, 'It's miles too big! We'll have to get another one done.' But they said it looked perfect - and padded it out with foam rubber. It had a Velcro fitting at the base, so when the wind machines were on the thing was still wobbling around."

I thought I was doing a load of rubbish, I really did Dave Prowse on making Star Wars

What was it like being on the Star Wars set? Did Prowse have any inkling of how successful the film would become?

"I thought I was doing a load of rubbish, I really did," he laughs. "You were wandering round looking at all these funny creatures and fantastic sets, but you had no idea what it would look like at the finish."

On The Empire Strikes Back, such was the level of secrecy that Prowse wasn't shown a complete script. His lines for the next day were sent by courier each evening.

For the big showdown between Luke Skywalker (Mark Hamill) and Darth Vader, Prowse wasn't even given the real lines. He had no idea of the big revelation until he saw the film at its premiere.

He recalls: "Suddenly there's me saying to Luke 'I am your father' - and I thought 'this is new!' I was sat behind Mark - who knew the real dialogue - and he thought I was going to jump over three rows of seats and smash him for not telling me."

For many years Prowse has travelled all over the world attending Star Wars conventions. His relationship with Lucasfilm, however, is not a happy one.

"We were about to start on Jedi and I got accused of giving information on what was going on in the movie. I didn't have a copy of the script, but somehow I got called a blabbermouth."

He denies any wrongdoing, but the rift has gone on for years. "I'm still part of the Lucasfilm family, although I appear to be a very distant relative."

Darth auction

Image caption The costume is thought to have been custom-made for the Star Wars series

The Darth Vader costume up for auction is being sold by American private collector who acquired it in 2003.

The auction notes say: "The costume is being sold on behalf of a gentleman recorded as having one of the most extreme cases of the debilitating condition Obsessive-Compulsive Disorder (OCD) ever diagnosed.

"The costume came into the gentleman's possession after much tenacity in his quest to possess an original Darth Vader suit from The Empire Strikes Back, as an aid to battle the condition."

The owner bought two suits from a UK company that had been authorised to create "second generation Vader suits for promotional purposes".

After examining differences in the second suit, the collector came to the conclusion "that he was now the owner of production-made helmet, mask, shoulder armour, and shin-guard components".

Christie's notes: "To say it is screen-used is difficult as there would be several production-made helmets, masks and shoulder guards, just to cope with the sheer intensity and requirements of filming."

Three masks and helmets have already been sold via Christie's in the 1990s. The seller is donating a percentage of the proceeds of the sale to Cancer Research UK in memory of his mother.

Jedi knight

Dave Prowse, meanwhile, is still acting in low-budget independent films.

Image caption R2-D2 actor Kenny Baker (left) and Dave Prowse (right) on the Elstree set of Star Wars in 1976

This year he appeared in The Kindness of Strangers - a film by first-time director Deborah Hadfield - which screened at Cannes. He will be working with her again next year in romantic thriller Sweetest Love.

As the interview ends, Prowse offers up an anecdote that not only sheds light on his first meeting with Sir Alec Guinness (Obi-Wan Kenobi), but also his thespian credentials.

"When Alec died, a biography came out and I got a copy and wondered if I got a mention. So I looked up myself in the index and there was a diary entry that said: 'Had lunch today with Dave Prowse - who is going to play Darth Vader'.

"And then there was a dash and the words - 'I fear he is not an actor'."

The Darth Vader costume will be auctioned as part of a Popular Culture: Film and Entertainment sale on 25 November, at Christie's, South Kensington.