Sudden pain on inside of leg just above right ankle. Hardly believable that it is a calf strain, but can't think what else it could be.
Had physio next day, and again 2 days later. Apparently one of the calf muscles attaches under the foot and goes up the inside of the leg - more like a tendon according to the physio. Had massage and taping of foot to ease the load on the muscle. Then the 2nd appointment it was taped again, including rock tape over that particular muscle. Seems to have worked, had a few twinges as I was warming up for the stair race, but then it was fine.