I did look this up a few months ago. I recall the nosewheel was lifted off at 80 knots and further acceleration took place in that attitude. Was never able to ascertain the "why". It was a procedure used on other British jets, the Vampire being one. The Vr concept was introduced after the first two Comet crashes, which were accounted for by the inability to accurately assess the attitude using the 80 knot procedure, leading to excessive nose high attitude with the result the drag never allowed the aircraft to accelerate to flying speed within the runway confines, or it became airborne in a stalled state.