They should have cucumber sandwiches, which would also cater for any vegetarians. There could be some with the crusts cut off for the posh people and some with the crusts on for everyone else.

I suppose these days they would have to have some sandwiches without butter for the vegans and some made with oatmeal biscuits, maybe, for those who think gluten is the work of the devil. But these options might not have been available in a real 1940s street party.