M0nica
Let me say it in words of one syllable or as near as I can. In this country we first started responding to terrorist attacks in the 1970s. It started with the IRA and extra protection of miitary and security sites.
Gradually, step by step, as various other terrorist groups established themselves and threatened us in new and different ways, we introduced new and different measures to meet these new and different threats.
None of this negates the fact that we first started introducing security measures in the 1970s to deal with the threat from the IRA.
I am sure in future more measures will be introduced if the nature of the hreats we get change, and may be some no longer used. As to where these threats come from, who knows. it could be Islamic based, or Extreme right wingers, or groups that at present we cannot imagine being a threat. Morris dancers, Boy Scouts or even the Boys Brigade.
Yes, and even way before that M0nica
However, I doubt very much that the three groups you mention: that at present we cannot imagine being a threat. Morris dancers, Boy Scouts or even the Boys Brigade. would be a threat. But you know that.
Terrorist and extremist groups consist of angry, disaffected, prejudiced people who have been radicalised by malign force.
How many of those persuading young people, even children, to become suicide bombers for some cause ever put their own lives in danger?