I was not intending to be discourteous, Mr Deputy Speaker.
The hon. and learned Gentleman said that it was not possible to screen out the correspondence of the various privileged groups he described. The issue arose at the Investigatory Powers Tribunal in respect of one of the Wilson doctrine cases, and that was the assertion made by the Government barrister at the time. However, I consulted a number of experts, including Ross Anderson at Cambridge, and they said that it was perfectly possible. A great deal of screening is already done to take out dross—issues such as pornography—and it is perfectly possible to screen out targeted groups as well.