It's Johnson's little whine about having to send the letter mandated by the Benn Act, purely for his fans and the over-excitable Sunday papers.

They in fact sent three: (1) a covering letter, (2) the letter you've posted above, and (3) the actual extension request. Johnson didn't sign the extension request, but legally that means nothing, and Tusk has accepted receipt of the request, says he's now acting on it, and has seemingly ignored the other one.

Here's the covering letter:



Here's the extension request:



The wording of the request is precisely as stipulated by the Benn Act.