Q. My wife’s daughter and son-in-law and their family live about 40 miles away. Whenever they come to stay, he asks if he can use an electric socket to charge his new Tesla. Although he thanks me profusely for making a socket available, he does not offer to pay for the electricity. Were he to do so, I would decline the offer, but I do feel that it is discourteous of him to take it for granted that it is a gift. How can I get him to raise his game?

– Name and address withheld

A. There is a protocol to deal with this emerging dilemma. Electric car drivers must make a point of carrying and brandishing cash so they can at least offer to pay for their charge. Even if hosts refuse the sum – typically £45 for an overnight charge of a Tesla – they welcome the acknowledgement inherent in the gesture. Next time, script another visitor to enthuse about the Tesla and go on to pleasantly probe about running costs while you stay silent –‘And what is the etiquette when you need to charge? Do you insist on paying your host? Or at least offer?’ This will put the son-in-law on the spot and force him to rationalise his presumptions.

Q. My landlord has kindly let me have a birthday party and out of joie de vivre and insecurity that everyone would say no, I have invited way too many people and they may not all fit enjoyably in the flat. I’m panicking now as my landlord hates out-of-control house parties. Can I disinvite some people even though they are all in overlapping friendship groups? Or should I cancel it all?

– C.G., London SW7

A. You can relax as the law of junior party-giving means that when the night rolls round, as many as 30 per cent of your invitees will, for flakiness reasons, be unable to attend.

Q. In what circumstances is it appropriate not to start/end a text or email with ‘Dear X’/‘Kind regards’ (or some such version)? With friends and family we often resort to ‘Hi’ and no sign-off, which is fine and informal, but at work (I am a solicitor) I feel compelled to address everyone properly. However, other staff routinely email or text without such an opening or closing. I feel uncomfortable with such informality at work. Any thoughts gratefully received.

– T.L., by email

A. The rule of thumb is that if an email is a substitute for a letter – formal solicitors’ emails usually are – then ‘Dear So and So’ and ‘Kind regards’ are right. If it is a substitute for a telephone or face-to-face conversation, informal is right. So you may come over as pretty stuffy if you put ‘Dear So and So’ to people in the office. Follow the style of greetings and sign-offs used by your colleagues – e.g. ‘Hi’ and ‘Thanks’.