There is a useful article on this subject in the August issue of "Which?" magazine. Conclusions:

- If you're making a contactless payment, it's best to take the card out and touch it to the reader, rather than just waving your wallet or handbag over it.

- A suitably-equipped ID thief could, in theory at least, read a card number and expiry date electronically, but not the cardholder's name or the security code.

- Wrapping a card in foil will keep it from being read, either accidentally or fraudulently.

Incidentally if your bank is like mine, you have to enable the card, using the PIN, before it can be used for contactless payments. If you don't want it enabled, you don't have to.