Complex sentence: Due to the gentleman's agreement with Scott, Mulock declined but unintentionally sparked off a rivalry by revealing to Shackleton that Scott was planning to "go south again"; it came as no surprise that in April 1908 Mulock failed to qualify as a torpedo lieutenant.
Split into simpler sentences: Due to the gentleman's agreement with Scott, Mulock declined but unintentionally sparked off a rivalry by revealing to Shackleton that Scott was planning to "go south again". It would come as no surprise that in April 1908 Mulock failed to qualify as a torpedo lieutenant.