Yes, Minister, Series Three (1982)

[Discussing possible reasons for the Prime Minister's early retirement]

Bernard:
Minister, I've heard something quite different.

Hacker:
What?

Bernard:
That there is £1 million worth of diamonds from South Africa in a Downing Street safe, but of course it's only a rumour.

Hacker:
Is that true?

Bernard:
Oh, yes.

Hacker:
So, there ARE all those diamonds in Downing Street!

Bernard:
Are there?

Hacker:
You just said there were.

Bernard:
No, I didn't.

Hacker:
Yes, you did! You said you'd heard this rumour, I said is it true, you said yes!

Bernard:
I said yes, it was true that it was a rumour.

Hacker:
You said you heard it was true!

Bernard:
No, I said it was true that I heard it!

Annie:
I'm sorry to cut into this important discussion, but do you believe it?

Hacker:
I believe I heard it. Oh, about the diamonds. No.

Annie:
Is it impossible?

Hacker:
No, but it's never been officially denied. First rule in politics: never believe anything until it's officially denied.