Complex sentence: Whilst the Monarchs of this era achieved little as a team, they did introduce Aussie Jack Young to UK speedway and he won the World Championship in 1951 as a Monarchs rider.
Split into simpler sentences: Whilst the Monarchs of this era achieved little as a team, they did introduce Aussie Jack Young to UK speedway. Young won the World Championship in 1951 as a Monarchs rider.