This cargo flight originated in Coventry, UK and it’s intended destination was Ireland West Airport, Knock, Co Mayo. In the event, poor weather conditions at Knock caused the commander to divert to Sligo Airport. Here, the weather was benign with Runway (RWY)11 in use. After touchdown the aircraft veered to the left and departed the tarmac surface onto the grass area, north of the runway. While the crash alarm sounded, as the Airport Fire Service (AFS) responded quickly, the Commander advised ATC that he did not require assistance and he steered the aircraft back on the runway and, thence, taxied slowly to the apron. On engine shutdown, an inspection showed damage to the left main wheel.