[Publius]

Another bit of Cockney rhyming slang.

"You aren't telling me pork pies, are you?"

Pork pies rhymes with lies.

[Lovely-Day-For-A-Guinness]

They don't like wasting words, so just "porkies" gets the point across.

Aris is one of their best - in Cockney it means "arse".