I've only just caught up with this story courtesy of Greg Hurt's STORY in The Times. This has all the makings of a huge scandal. As David Davis says in his letter, it has been convention since 1966 that MPs are not bugged. If Sadiq Khan was indeed bugged, on whose authority was it done? There are only four possibilities...
1. It was authorised by the Head of Mi5 with no reference to a politician
2. It was authorised by the Home Secretary (Khan is her whip!)
3. It was authorised by the Justice Secretary (unlikely)
4. It was authorised by the Prime Minister
Which is it?