Underground mice

SIR – What has happened to the tiny black mice that used to dart about the track beds of London Underground stations? Two years ago, I used to see them every time I travelled. In the past few months, I have seen none.

Have they starved during lockdown? If so, will Transport for London take steps to reintroduce them? Over the decades, they must have raised the spirits of millions of commuters.

Nick Baxter

London SW11