Career
Thomsen first rode in the United Kingdom with the Wolverhampton Wolves. Signed by Len Silver for the Hackney Hawks in a swap deal with Dave Morton, becoming team captain in 1980. When the Hawks closed at the end of the season 1983 he then retired from British speedway and then to Spain in 1989.
He rode for Swindon Robins in 1986.
Individual World Championship
1977 - Göteborg, Ullevi - 5th - 10pts
1979 - Chorzów, Silesian Stadium - 10th - 6pts
1980 - Göteborg, Ullevi - 10th - 7pts
World Pairs Championship
1976 - Eskilstuna, Eskilstuna Motorstadion (with Ole Olsen) - 2nd - 24pts (8)
1978 - Chorzów, Silesian Stadium (with Ole Olsen) - 3rd - 21pts (5)
World Team Cup
1979 - London, White City Stadium - 2nd - 31pts (4).