Just guessing but maybe she wants a quick getaway in case Philip is actually on his last legs. Do the speech, jump in the motor and away.
Or armoured car in case some sweaty oik runs out of the crowd with a knife.
The apple doesn't fall far from the tree... My mate's mum was the housekeeper at the Queen Mum's best mate's place in Chelsea... She'd be up there a couple of times a month to watch the horses on TV and drink gin...
Just guessing but maybe she wants a quick getaway in case Philip is actually on his last legs. Do the speech, jump in the motor and away.
Or armoured car in case some sweaty oik runs out of the crowd with a knife.