After serious thinking Harold Davis wrote :
Very quick question: removing the (cross type) tap handle on a kitchen hot
tap, while leaving the headgear untouched, doesn't get me wet, right? I'm
wondering whether I can help an elderly friend of mine by changing the
skirt piece that covers the top of the headgear in two minutes flat without
going up into his loft.

The cross, usually has a screw in from the side, though some have the
screw in line with the spindle. The cross might be well seized on, so
wood wedges between cover and cross might help, plus a soft mallet.

No need to turn the supply off.