How do I delete iCal data from iCloud?

Ok, so I'm hoping this will be an easy one.

I sync'd my iCal with iCloud, and somehow have got duplicates for every entry going back decades.

I've done the old un-tick the iCal box in iCloud prefs, and deleted from my Mac.

I've also unticked the same setting in my iPhone and iPad, so now I'm showing no appointments anywhere on my devices, but double entruies on the cloud server.

I've managed to find a previous library of Calendar appointments using Time Machine, so I'm showing the correct diary on my Mac, but before I re-tick the sync box in iCloud prefs, I want to delete all the entries on the iCloud server, then I'll just move all my appointments to the cloud (once) and then on to my other devices.

Anyone help?

Thanks.

Bob.