This is what Paul has, Dupuytrens disease, he's had an operation on his hand to correct what Wiki describes as " a fixed flexion contracture of the hand where the fingers bend towards the palm and cannot be fully extended
(straightened). It is an inherited proliferative connective tissue
disorder which involves the palmar fascia of the hand. It is named after Baron Guillaume Dupuytren, the surgeon who described an operation to correct the affliction in the Lancet in 1831."
Paul made 3 posts on his Facebook, this one showing his hand after the operation