The would-be intruder should be pleased that the soldier's rifle was (probably) not loaded. When I did my National Service, in the Army, we were not given any ammunition for our rifles when we were on guard duty, although we had to patrol with fixed bayonets when there was once an IRA scare.
Well done that man.
Despite the misconception that HM Foot Guards are 'just there for show', they do in fact take the duty of guarding Her Majesty with the utmost steadfastness.