My name is Mark Smith. I'm a journalist and I'm on a mission. A mission to talk exactly like presenters do in television documentaries.

The first thing I must do is call everything a "mission", or a "quest", or a "journey", even though what I really mean is a "television programme".

I must then speak in - a - very - slow - halting - voice and put emphasis on certain WORDS for no apparent reason.

Talking like that will be very annoying, especially when I keep it up for an hour, but it must be done to prevent viewers spotting that the documentaries themselves are a bit rubbish.

Documentaries such as this one: Dead Famous DNA[ (Channel 4, Wednesday, 9pm), which was presented by Mark Evans, a vet and a regular on animal programmes.

"My name is Mark Evans," he said. "I'm a scientist and I'm on a mission to hunt down the DNA of the most famous people who ever lived."

The first of his targets was Elvis Presley and the conclusion of the programme, or mission, or quest - after three years of research and a team of scientists working on his DNA - was that Presley had an obesity problem.

Who knows what other revelations about dead famous people will follow that one?

Perhaps we'll learn that Winston Churchill liked cigars, Albert Einstein was clever, and Leonardo da Vinci could paint.

As for Elvis's DNA, for some reason Evans seemed to be stunned by all the non-revelations he kept non- discovering.

After finding some of the singer's hair, for example (it had been kept by a barber), it was sent to scientists who extracted the DNA and found variants that can cause obesity as well as migraines and glaucoma.

Evans appeared to be taken aback by this even though Elvis's health problems, including the migraines and glaucoma, have been in the public domain for years.

As for his obesity, it's so well-known, it's a cliche; but Evans - an experienced vet but also, apparently, a man with no access to Google - gawped at the news about Elvis's weight problem with the startled expression of a trainee vet performing his first rectal examination of a cow.

The rest of the programme was no better, especially when it tried to stoke up the idea that it was doing something controversial.

Why on earth should DNA be controversial?

Decoding it is a scientific technique like any other, but the programme suggested applying it to dead famous people's hair or toenail clippings could uncover something of depth about them.

"Could DNA reveal why Marilyn Monroe was attractive?" asked Evans, "Or why Einstein was so intelligent? And Hitler so evil?"

Well no, it couldn't, and it was stupid to suggest otherwise.

As one of the scientists in the programme said, there is nothing that can be learned from Hitler's genome about why he killed 51 million people.

The fact that Dead Famous DNA pretended the opposite made it a fatuous, vacuous programme posing as a profound scientific mission.