CD and B73: is that the right question? I think that strikes to "why did X send a text to the pilot saying Battersea was open when in fact it was not open?".
From the point of view of the pilot, it seems that he received a text saying Battersea was open. Even if that was factually incorrect, he pilot did not know that and he proceeded to act upon that information by asking Thames Radar about the option of diverting, and dropped down below the cloud-base to hold below in anticipation of being accepted into Battersea.
Puntosaurus: Thanks - I think this is a valuable point for me to take on board. It is a different matter to plan for diversions whilst on the ground compared to an environment of congested airspace / bad weather / client pressure. Though circumstances may make that scenario unavoidable, I need to be conscious of the need to take steps to reduce my workload and risk if I am to divert resource (my attention) to assessing / planning the diversion. I can make that part of my rehearsed response to in-flight "surprise".