Dear Mary: How can I catch a ‘re-gifter’ out?

Q. I live in a small house in Hampstead and have taken in a friend of a friend as a lodger. He pays me a reduced rent for use of one of my spare bedrooms. I like him, but the agreement was that he would occupy the room for two nights a week; this, however, has started to slip into him being there for three, and often four, weeknights each week. I am livid but don’t know what to say to him. Neither I nor the friend who put us in touch with each other has any idea whether he is taking advantage of me or has just become forgetful. He is a widower. How do you think I should tackle this? 

– S.M., London NW3

A. Collude with an imaginary friend (let’s call her Bertha), who will play ball to help you solve this dilemma. Next time you see your lodger, gush brightly that, by the way, your friend Bertha is desperate for a lodger two nights a week. Similarly to yourself, she doesn’t want someone for more than two nights a week but if he is finding that it might actually suit him to spend four nights a week in London, would he be interested in going there on top of keeping his room with you? If he says yes, then Bertha can say that sadly she has already found someone else. The point is to re-establish the boundaries, as you would with a teenager, and this would be a friendly way to send a warning shot across his bows.

Q. I want to know if my expensive birthday gift of Fortnum’s chocolates, which I always give to my dear brother, is being regifted by his parsimonious wife. How can I catch my sister-in-law out?

– K.W., London NW1

A. Why not conceal an Apple tracking device in the box? If your brother is the one to find it then he will ring you and have a laugh. If not, your suspicions will be confirmed.

Q. I travel up to London for pleasure every six weeks or so with another woman of similar age who lives nearby. When we get to Paddington, I like to take a black cab, partly because I like the banter and also because I don’t like using the Tube. My companion usually comes on board the taxi, as we are both heading to the West End or to Sloane Square, but I sense she can’t really afford this method of getting around London. I can, but I feel it would be patronising not to stick to going halves on the cost. Can you suggest anything? 

– Name and address withheld

A. Tell her your accountant has mentioned that if you remember to get a receipt from the cabbie, your taxi fares can be set against tax. She is therefore more than welcome to join you in your taxi without contributing to the cost.