In general body snatching has a bad press - but this was different. Rather than plundering graves for profit, we would expose a mass grave hiding illegally shot dogs.

We had set out to uncover corruption, now we had found a graveyard near a kennel that could reveal the fate of some of the 10,000 dogs that retire from racing each year.

So, we found ourselves cramped into the back of a transit van dressed in paper boiler-suits, masks and marigolds, waiting to start digging under cover of darkness.

All this despite knowing whoever shot the dogs might just discover us.

Sawn-off rifle

Kennel owner and trainer Steve Davis, claimed former workers, had killed dozens of greyhounds with an unlicensed sawn-off rifle.

They said he saw greyhounds as a commodity and simply shot them once they were too old or injured to race.

Armed with shovels and garden forks, Paul Kenyon, myself, the assistant producer and the director scrambled through the woods next to the Kennels in Oxfordshire.

We agreed simple rules - no torch light near the owner's house and no verbal communication - 30 seconds later cracked twigs and whispers set over 100 kennelled dogs barking loudly enough to wake the dead.

Fortunately dogs barking at night must be the least suspicious event in a kennels, as no one came out of the house or any of the other staff buildings.

The Kenyon team are not used to physical labour. We have muscles trained on lifting dinner forks rather than the garden variety. The freshest graves had been buried under a 20 foot pile of earth and were too much for us.

Foul smell

We started on an older pit and soon drops of sweat were making lines through the foul smelling dirt stuck to our faces. Then I spotted the yellow ivory of a greyhound's jaw poking through the earth.

A dog's skull unearthed from the grave

It was a dog aged between three and five-years-old; the age when greyhounds are too old to race. Thousands are killed each year because they no longer pay their way - their lives often ending several years before they would die naturally.

Greyhound racing is a sport seeking to reinvent itself as an ideal night out for the family and as corporate entertainment - and at many tracks it has succeeded.

However, rumours of shady dealing persist and we felt they needed to be investigated. Greyhound racing is a closed world that is difficult to crack, so we had to pass ourselves off as owners and trainers.

Greyhounds have an amiable temperament and are easy to get on with. Getting a greyhound to run is easy, they love to run - so much so that getting them to stop is a lot harder.

Cocaine

I wasn't the only one who suffered the humiliation of chasing a canine athlete - capable of 40 mph - in an attempt to get it to come back. It's lucky tracks are oval - they do, eventually, come round again.

It was these months of hard work and humiliation that eventually opened up the greyhound world to us, revealing race fixing at a major track and drugging dogs.

We got access to a drug dealer's inner sanctum and found a variety of substances - drugs to make dogs go faster, drugs to make them go slower and even drugs to kill them.

"So what is the best substance to fix a race?" we asked him. He pulled out a bucket full of silver wraps and said it was cocaine.