Zapped a mk5 cortina that was blinding me from behind with one of them 55W lamps - blue lights immediately!I thinks that's exactly all what standard lights are supposed to only be capable of - hence the 21W max rating.
You could buy a 55W halogen bulb with the same fittings at the 21W bulb in the USA - I still have a couple from 20 yrs ago . . I never dared fit them for fear of melting the lenses.
I used to fit a 100W fog lamp under the back bumper - swing it up and switch it off for MOT time. Very useful in the back of beyond when the navigator works out we've gone wrong for the next check-point. Now I just have a couple of 5W LEDs lamps either side of the tow bar - lights the whole front of the house up when I reverse in the drive.
Yes sir, sorry officer, will change it immediately - not..