Dear Mary: How do you stop a cat from sneaking next door?

Q. A great friend is in a terrible state regarding a cat foisted on her by a close relation. She has become very attached to it but it keeps going next door through her neighbour’s cat flap and eating the neighbour’s cats’ food. The neighbour is a high-profile elderly lady who is getting annoyed. My friend, who is supposed to be getting on with her next book, is now reduced to standing with a water pistol ready to squirt her cat if it tries to enter the neighbour’s house. My friend has offered to pay for a digital cat flap but the neighbour has replied that in the warm weather she will be leaving her garden doors, not just the cat flap, open. Moreover she leaves ‘wet’ food out all day and apparently this is very tempting. Any advice, Mary?

– E.S., London W11

A. A professional cat expert has lent his intelligence to this query: ‘Most cat-lovers/owners relish and respect the fact that cats are ungovernable and unbiddable, and that is their charm.