The Chilcot Review on Intercept as Evidence considered this issue and concluded,
“that a limited number of new successful prosecutions would be made possible by the use of intercept as evidence. The UK already achieves very high rates of successful prosecution of serious criminals and terrorists; there is limited room for substantial further improvement in such cases through the use of intercept as evidence”.
The review's conclusion on this issue was informed by the views of a number of senior judges and lawyers. These included the Attorney-General's Office, the Crown Prosecution Service, the Treasury Solicitor, Sir Igor Judge, Sir Brian Leverson, the Lord Chief Justice, Nigel Sweeney QC and Stephen Williamson QC.