I am sure my husband picked up a sexuallytransmitted infection while on a business trip to Brussels and was treated on his return. Could I go to our doctor and get him to tell me?

No, Your general practitioner is not allowed to disclose anyone's medical history - even to a spouse. Also, GPs don't normally treat STIs, so your doc is most unlikely to know whether your husband had an infection.

Treatment would almost certainly have been at a genito-urinary medicine (GUM) clinic.

My advice? Ask your husband to tell you the honest truth. And go to a GUM clinic yourself for a check-up.