A blind grandfather who had suffered two strokes was shot with a Taser gun when a policeman mistook his white stick for a Samurai sword.

Colin Farmer, a retired architect aged 61, feared he was about to be mugged when he heard a shout as he “shuffled down an alley”. As he tried to get away the officer shot him with a barb carrying 50,000 volts.

Police had been sent to Chorley town centre, in Lancashire, on Friday after a report that a man had been seen roaming the streets with the sword.

Mr Farmer said: “I felt this huge electric shock . . . It was like being plugged into the mains. There is no excuse for attacking a registered blind and disabled man