Until this morning the forms on the website could not be submitted. They all produced an error stating that their content was spam. Nothing could be further from the truth. The cause was an incompatibilty between two plugin apps.
It took me the best part of this morning to figure out what happened and to fix the problem. Half an hour ago I tested the forms myself. All of them now seem to function normally again.
My apologies for any inconvenience this situation may have caused.