The JPs concerned were well ahead of their time. Specifically, HRH's jets (the Mk VIs I believe) had a small hydraulic hatch in the top of the nose cone that opened as the nose wheel came under pressure (usually on landing!) and pushed up a small flag with the Royal Crest on it.
Also, the main tyres were solid (rather than gas filled) so that they would be invulnerable to unexpected attacks by Bull Terriors!
I'll get me coat!
Sorry, I meant 'terrier' ... I'll get me hat and gloves!