The arm is probably the original as I've had the car since 2003 when it was just one year old. It's done over 101K miles and the wear & tear took its toll. I checked this arm a couple of months back and there wasn't any play, ball-joint cover intact and plenty of grease. I replaced the other one about 4 years ago as the balljoint cover had gone.
Luckily it went as we pulled up to the fuel pump and not the 40-50 mph drive via country lanes to the garage!
thanks to the AA for saving the driveshaft (he removed it on the forecourt) and getting the car back home so I can fix it.