70s skit - "I hope you've sealed the envelope properly"

Question

In 1985 the inimitable Patricia Routledge did a series of five short sketches for the BBC where she plays a woman named Kitty. Practically every sentence is a (pop) culture reference and I've been able to figure out most of them, but this one especially remains a mystery.

The video can be found here: https://www.dailymotion.com/video/x2pfkk1

She said, ‘Its Morag from the television programme, do you remember me?’ I said, ‘Yes, I do; I lent you two cotton buds which I never saw back.’ She said, ‘I’ve got the producer for you’, so I said, ‘I hope you’ve sealed the envelope properly’, which is an old golfing retort of mine. On she comes - the producer - I could hear her boiler-suit creaking even long-distance - ‘Is that Kitty?’ I said, ‘If it’s not, this cardigan’s a remarkably good fit.’ She said, ‘Kitty - do you like fun?’

What does this expression mean? The context is that she's on the phone about to have a conversation with a stereotypical dungaree-wearing, chain-smoking lesbian television producer.

Answer 1

This is a reference to the 'envelope rule' used in golf foursomes, most famously in the Ryder Cup. Where a player suffers an injury, another player can be called upon to sit out. Their name is placed in an envelope that both captains verify is firmly sealed.

I've no idea why it's funny though, other than she's using it as shorthand for suggesting that the female producer is the sort of woman who would be the captain of a golf team (e.g. a stereotypical lesbian).