This was told to me as a true story. In the 1980s an official of the intelligence services of the Irish Republic had lunch with the eighth assistant cultural attache at the British embassy whose true job function was well known to them both.

"OK," says the Irish guy, "you've had your fun - but I'm letting you know that your Gaelic-speaking agent who has been listening in to all the conversations at IRA pubs in Co. Donegal is known to us. He got drunk or careless and started arguing back."

"Oh all right," says the British guy. "Just between friends, though, how did you know? Our people swore to me that his Gaelic was absolutely perfect."

"It was. But not that many speakers of perfect Gaelic are black."

Heh. I originally heard that one regarding a CIA agent in Siberia.

My Dad told me the Jones-the-spy joke, but he can't do a Welsh accent, so he did an Irish one instead ("No it's Jones the spy you're looking for, to be sure, to be sure").

That would bring a whole new dimension to it.

I like telling this Glaswegian joke in an English accent:

What's the difference between Bing Crosby and Walt Disney?
Bing sings and Walt disnae.