I'm most grateful to Mary Yeoman for offering this simple solution to my heirloom/heritage tomato problem (see previous post).
She wrote: Put them in a brown paper bag with a few banana skins and one or two ripe bananas and I can assure you they will ripen in a few days.
They (beef tomatoes) are always the last ones to ripen.
I've looked this up and Mary is absolutely correct. Bananas release a gas called ethylene, which is a natural ripener. Apparently professional tomato growers use it, together with temperature control, to regulate their ripening. It's one reason why shop bought tomatoes never taste nearly as good as home grown. But I'm afraid I've no choice: with steam rising from my greenhouse and the grass outside thick with frost, it's bananas or bankruptcy for me. Thank you, Mary.