There's no law against recording a stop and search, and police forces have been regularly advised by ACPO to allow this kind of monitoring of their duties (as long as the person recording does not attempt to interfere). The Met have a statement about this on their website:

Members of the public and the media do not need a permit to film or photograph in public places and police have no power to stop them filming or photographing incidents or police personnel.

However, the reality is that even officers of a reasonably senior rank, such as this Inspector, are not happy for them and their colleagues to be recorded, and will do everything they can to prevent it: