Diff wound up?

My uncle's got a R reg 90 and played in the snow on the roads and put it in to diff lock. I think he must have driven on tarmac too long in that mode with out disengaging it. He says that when he say pulls out of a turning he gets a shuddering.I had a trooper that done that.I told him to reverse it a long way to see if it would come out . No joy so i said turn it hard round and back up in a circle .No joy . I think the light is on, on the dash any suggestions on whats gone wrong and how to sort would be grateful.

Jack it up, keeping anything vital away from the front wheels??

Check that the linkage has actually disengaged? Me mates Disco the pin came out of the lever and he was stuck with the difflock on. Fortunately I found the pin stuck in the oil & ****e on the box and managed to refit it without having to dismantle anything. does the RR have a lever or is it electrically operated?

It has a lever. will give him a bell and get him to have a look for the pin Thanks