A Boeing 777 aircraft was scheduled to fly from London Heathrow to Los Angeles. During taxi to the holding point, the crew received a change to the weight, which was then correctly entered into the Flight Management Computer (FMC). V speeds were set to 154 kt, VR: 161 kt, and V2: 167 kt. The aircraft was following a Gulf Air aircraft which was cleared to line up and was passed a surface wind of 180ø/15 kt with infrequent gusts of 28 kt. Following the departure of one aircraft ahead, the Boeing 777 was cleared for take off. The crew lined up the aircraft and with the first officer handling the controls, a rolling take off was commenced. Left bank control input and right rudder were required to maintain the runway centreline and some crosswind yaw was experienced but it was not considered to be significant. Acceleration was normal and approaching V1 of 154 kt there was an 8 to 10 kt reduction in airspeed which steadily restored to its previous value, and rotation was initiated at 161 kt. All three crew members considered that the rate and angle of rotation was normal, and the aircraft was accelerated towards V2 of 167 kt. The crew then received an Engine Indication and Crew Alerting System (EICAS) message that the aircraft had suffered a tail strike. The aircraft was depressurised in accordance with the emergency checklist and climbed initially to FL 90 and then held at Daventry at FL 70 where 130,000 lb of fuel was jettisoned to reduce weight for landing at Heathrow. The emergency checklist was completed and the aircraft was given radar vectors for Runway 27L at Heathrow where an uneventful landing was carried out. There were signs of runway contact on the underside of the fuselage from about Station 2130 to Stn. 2274; a total length of some 3.65 metres (12 feet). At Stn. 2150 (pressure bulkhead) and at most of the frames as far back as Stn. 2268 the outer skin had been completely abraded away on the fuselage centreline. The tail strike sensor at Stn. 4041 had been abraded away by about 50%.A Boeing 777 aircraft was scheduled to fly from London Heathrow to Los Angeles. During taxi to the holding point, the crew received a change to the weight, which was then correctly entered into the Flight Management Computer (FMC). V speeds were set to 154 kt, VR: 161 kt, and V2: 167 kt. The aircraft was following a Gulf Air aircraft which was cleared to line up and was passed a surface wind of 180ø/15 kt with infrequent gusts of 28 kt. Following the departure of one aircraft ahead, the Boeing 777 was cleared for take off. The crew lined up the aircraft and with the first officer handling the controls, a rolling take off was commenced. Left bank control input and right rudder were required to maintain the runway centreline and some crosswind yaw was experienced but it was not considered to be significant. Acceleration was normal and approaching V1 of 154 kt there was an 8 to 10 kt reduction in airspeed which steadily restored to its previous value, and rotation was initiated at 161 kt. All three crew members considered that the rate and angle of rotation was normal, and the aircraft was accelerated towards V2 of 167 kt. The crew then received an Engine Indication and Crew Alerting System (EICAS) message that the aircraft had suffered a tail strike. The aircraft was depressurised in accordance with the emergency checklist and climbed initially to FL 90 and then held at Daventry at FL 70 where 130,000 lb of fuel was jettisoned to reduce weight for landing at Heathrow. The emergency checklist was completed and the aircraft was given radar vectors for Runway 27L at Heathrow where an uneventful landing was carried out. There were signs of runway contact on the underside of the fuselage from about Station 2130 to Stn. 2274; a total length of some 3.65 metres (12 feet). At Stn. 2150 (pressure bulkhead) and at most of the frames as far back as Stn. 2268 the outer skin had been completely abraded away on the fuselage centreline. The tail strike sensor at Stn. 4041 had been abraded away by about 50%.