Labrador for Sale

Thanks to Estelle for this one:

A man is driving around a remote area of Cornwall and he sees a sign in front of a broken down shanty-style house: 'Talking Dog For Sale ' He rings the bell and the owner appears and tells him the dog is in the backyard..

The man goes into the backyard and sees a nice looking Labrador retriever sitting there.

'You talk?' he asks.

'Yep,' the Lab replies..

After the man recovers from the shock of hearing a dog talk, he says 'So, what's your story?'
The Lab looks up and says, 'Well, I discovered that I could talk when I was pretty young. I wanted to help the government, so I told MI5... In no time at all they had me jetting from country to country, sitting in rooms with spies and world leaders, because no one figured a dog would be eavesdropping.'
'I was one of their most valuable spies for eight years running. But the jetting around really tired me out, and I knew I wasn't getting any younger so I decided to settle down. I signed up for a job at Heathrow to do some undercover security, wandering near suspicious characters and listening in. I uncovered some incredible dealings and was awarded a bunch of medals.' 'I got married, had a load of puppies, and now I'm just retired.'

The man is amazed. He goes back in and asks the owner what he wants for the dog.

'Ten pounds,' the man says.

'Ten pounds? This dog is amazing! Why on earth are you selling him so cheap?'

'Because he's a liar. He never did any of that stuff.’