Japan was surprised by the gas attack mounted by Aum Shinrikyo, but Scotland Yard found the Mohammedans' Holy Ricin of God before they could use it on anyone. I've seen some pique expressed about shaggy sheikhs slipping through police cordons in London, but the piquerati don't always consider that perhaps there was a reason that the personality of interest slipped away ...... or may have been allowed to slip away.
If I were a London police inspector sincerely interested in meeting all the sheikh's special friends, I might let him slip away to go visit a few of them. Then I could visit them, too, and we could all get to know one another.
Too, people who compare British security unfavorably to France's need to reflect on how many North African Moslems are living in France, and how many attacks on Jews there have been in the two countries, comparatively.
That's precisely what happens. What people don't realise is that every time the radical Islamists speak up in public, there's a policeman at the back of the crowd quietly taking down names and taking photographs. We have, by this method, prevented attacks on Britain.
Regards, Ivan