The Sweeney star plays a man diagnosed with the devastating condition, which causes severe memory loss and confusion, and his new-found knowledge of the illness meant he spotted signs of the disease in an old man he found walking the streets near his home in rural Essex, England.
He tells British newspaper The Daily Mirror, ""I saw this old boy wandering alone. It was a cold day and he was only wearing a vest. I though, 'He doesn't look well,'... I just had a feeling. I didn't approach him, I didn't want to scare him. So I rang the Old Bill (police) and they came and got him.
""It turned out he'd wandered off. They found out who he was and took him back. Before I wouldn't have questioned it - I'd have just thought, 'Silly b**tard'.""