"Security chiefs say the power is an essential tool in cases where there is intelligence that someone is involved in extremism but has not yet committed a crime, such as someone associating with known plotters" .... from BBC News
www.bbc.co.uk/news/uk-12283114
So its now not just a crime to be "thinking" about something ... its a crime to know someone who might be "thinking" of something ?
They are digging themselves into an even bigger hole !
The Common Law has managed to do a very good job for more than 1000 years - providing all the rights that the State needs, through Civil War, 2 World Wars etc - I see no reason whatsoever (other than providing spurious people with spurious jobs) to extend it.