In response to Conservative MP Aidan Burley's tweets that this was "the most leftie opening ceremony I have ever seen", a Downing Street source has told me: "We don't agree with his views."
More top news
See how your area fares.
The world's first ever 'hole in the wall' was installed in Enfield, north London, on June 27 1967.
America says it has "identified preparations" for an attack similar to that which killed at least 86, including 30 children, in April.