Image caption Tom Six has screened the film at various film festivals around the world

One of the more controversial movies of the summer is niche horror The Human Centipede (First Sequence).

Written and directed by Tom Six, the film tells the story of a demented surgeon who kidnaps tourists to use for his bizarre experiments.

The publicity material for the film quotes tabloid headlines like "Is this sickest film ever made?" and trumpets in underlined capitals: "IT IS 100% MEDICALLY ACCURATE!"

Set in Germany, The Human Centipede sees the surgeon (played by Dieter Laser) surgically connect two young American women (Ashley C Williams, Ashlynn Yennie) and a Japanese man (Akihiro Kitamura) into conjoined "triplets".

It's enough to say that they share a single digestive tract. Free sick bags were given out at a recent press screening (although none were put to use).

Dutchman Six started his career in television as one of the original directors of Big Brother in the Netherlands.

Here he explains the challenges of getting his project made, and why he has chosen to shoot the sequel The Human Centipede II (The Full Sequence) in the UK.

How do you raise the money for a film like this?

They thought I was a European lunatic, so they left Tom Six on the US auditions

It was quite tricky. We produced three films in Holland before so we had this small group of investors - we approached them again and said we are going to make an international horror film and it's about a surgeon who stitches people together, but we left out [some details] because we knew if we mentioned those things they wouldn't have financed it.

When the film was finished they really loved it, so we got away with that. But otherwise the film wouldn't have been made.

How difficult was the casting process?

We did the auditions in New York for the American girls, and we got a lot of beautiful actresses to the audition.

I made a drawing of the human centipede construction - and because a picture says more than a thousand words. I showed the drawings to the actresses and so many became very angry with me. They thought I was a European lunatic, so they left.

The smart ones stayed because I explained how I was going to shoot it. We ended up with the great Ashlynn and Ashley. A lot of actresses only want to be pretty in films - and this is something different.

What will mainstream audiences make of it?

I was in the audience at the American premiere. I got all kinds of reactions. I saw people vomiting, people left the theatre because they couldn't handle it. I had a girl who was too afraid to talk to me afterwards, she thought I was totally nuts.

Image caption A Centipede sequel is due to shoot in London

In Japan they laughed during the whole film - they couldn't stop laughing.

How funny did you intend it to be?

Not at all. I have a really dark sense of humour myself. But when I wrote the script I wanted to be really serious, but that seriousness creates some humour somehow.

The whole set up is identical to the Rocky Horror Picture Show. Was that coincidence?

I wanted this film to use all the horror cliches - the flat tyre, the phone not working, the naive girls getting into trouble...

I knew if I started the film like that it would trick the audience, because they think 'yeah yeah we've seen this a thousand times' and then - BAM!

How uncomfortable was it for the actors?

For about half of the shoot - two weeks - they were on their hands and knees. They got back and neck problems so we gave them a massage every day. The special effects people made a construction that each time we finished a shot they could easily stand up again, but it was pretty tough on them.

Is there a deeper message to this film?

I read a lot of books about World War II so when I wrote the story I kept referring to the terrible things the Nazi doctors did, and I put in American and Japanese characters so they are all related to the main players of the Second World War.

Why set the sequel in the UK?

We start shooting mid-August in London with an almost entirely British crew and cast.

When I talk about the main players in World War II, a lot of people ask 'where is England?' I wanted a film in the English language and I absolutely love London.

The sequel's title hints at a longer centipede - is that correct?

Yes, the centipede has 12 people. I had so many ideas when I wrote part one but I couldn't put them all in because I wanted the audience to get used to the sick idea. Now I can put all my crazy ideas in part two.

What other projects do you have?

I really want to explore the horror genre some more, so I would like to shoot a film in LA - a very controversial film. I can't say what it's about yet. I'm writing the script right now.

The Human Centipede (First Sequence) is released in cinemas on 20 August.