Olympian Linford Christie's milk run collision
The former 100m champion allegedly clambered from his damaged Audi A8 after the collision and appeared to go into shock, rolling on the ground.
Witnesses later recalled him saying: "Oh my God, it's all my fault," jurors were told.
Aylesbury Crown Court heard the 51-year-old set off to buy a pint of milk from a Tesco Express garage and was driving back to Amersham, Buckinghamshire, when he found himself on the wrong side of the A413.
Seconds later, his car - with the number plate 100 RUN - hit the silver Mercedes travelling in the opposite direction, it was alleged. The taxi was propelled onto a grass verge, while the Audi came to a halt in the middle of the carriageway.
Christie, on his way back to his girlfriend's home, was able to walk from his vehicle but newlywed Peter Ashton had to be dragged from the taxi after the late-night crash on 8 May last year.
Prosecutor Nigel Ogborne said Mr Christie had failed to buy his milk that evening because the petrol station was closed and was on the way home at about 11:40pm when he ploughed into the taxi.
"He drove for some 185 metres andhe drove on the wrong side of the road," Mr Ogborne said.
"He was driving on the opposing carriageway and a car was driving the other way and there was a head-on collision."
Christie, who was in court, denies dangerous driving.