[2] Tweddell won the Amateur Championship in 1927, beating Eustace Landale 7&6 in the final.

He was in seventh place in the qualifying but started with a disappointing 78 in the championship itself, and finished tied for 30th.

[6] Tweddell was selected as the playing captain of the British 1928 Walker Cup team.

The match was played at Chicago Golf Club and resulted in an 11–1 win for the American team.

Tweddell reached the final of the Amateur Championship in 1935, losing to the defending champion, Lawson Little.