As people have said, "dinner" is usually the evening meal. But with the vast bulk of British working class people — although changing now — "dinner" was usually the midday meal. "Lunch" has been in increasing usage over the last half century. Although I knew of the word as youngster — probably from TV — I recall hearing it for the first time from a scout leader. I was sufficiently astonished by its usage to remember it even now.

The midday meal school supervisory staff are called "dinner ladies", although I presume "inclusiveness" has changed that. The evening meal in ordinary parlance is often confusingly referred to as "tea"...

I regard calling the evening meal “dinner” as something of a middleclass affectation, and so simply refer to my last main meal as my “evening meal”…