A funny little info from TV2 - The two colour-guards are identical twins.
There are of course many families for whom it's a tradition to serve, in this case, in the Coldstream Guards.
This parade has been honoring the British monarch since 1748, albeit with few breaks during WWI and WWII.
The rifles they use are Lee Enfield 85, 5.56, with the sights (that are more expensive than the rifles) covered up. The design with magazine behind the trigger, is called Bull-pup, and as such the rifle can be much shorter than those with the magazine in front of the trigger.
Even though that makes the triggering mechanism a little more complicated, the compact design makes the rifle very well suited for using inside an infantry fighting vehicle (IFV) and also very well suited for airborne troops.
As a little curiosum, during the First Golf War, the Americans leaned that the British army had shipped hundred of thousands of condoms. And try as they might, the Americans couldn't spot any women in the desert! In turned out the condoms were used to pull over the barrel, preventing sand from getting into the barrel.