What are these guys ON?

This arrived late January. They didn't waste much time,the poor loonies. Note the underlining of the deadline,as if their silly bit of paper amounted to some kind of threat.
The other documents were the contract for the American rights offering me $1(US!).

Sending it by Recorded Delivery was a purely gratuitous insult to my integrity.
They probably wanted to play tit-for-tat yet again for my sending the claim to their solicitor.

Pathetic!