Complex sentence: He retired from international football in 1998, his last match being a European Championship qualifier against Estonia on 10 October 1998, at the age of 40 years and 78 days, which set a new record as the oldest player to play for Scotland.
Split into simpler sentences: He retired from international football in October 1998, at the age of 40. Leighton set a new record as the oldest player to play for Scotland.