Dear Mary: I received a ‘save the date’ – but no formal invitation

Q. Fewer people carry cash. The traditional pourboire is at risk. I am bored with lending money to our otherwise lovely house guests. Would it be unmentionably vulgar to install simple swipe card machines in the spare bedrooms? Please advise, I would be grateful.

– N.C., Stanton St Bernard, Wilts

A. Swipe machines are not the answer. There are two categories of likely offenders here. One: people under a certain age are often unaware of the custom of tip-leaving. They need to be told. Two: guests who are aware but never carry cash, then suffer from post-hospitality remorse when they forget to pick some up and have to leave without paying their dues. It would be kinder to both categories to say – when firming up – something along the lines of: ‘Oh by the way, our nearest cash machine is now 15 miles away (exaggerate) so don’t forget to stock up before you come as it’s such a bore having to go out for it on the day you are leaving.