He competed in the steeplechase at the 2005 World Championships in Athletics but did not progress beyond the heats. He returned for the 2007 World Championships but again did not go past the heat stage. He made the world championship team after running 27:57 in the 10,000m at Brutus Hamilton Invitational on the track. Lemoncello ran in the senior race at the 2008 IAAF World Cross Country Championships and finished in 78th place. He represented Great Britain at the 2008 Summer Olympics, again being knocked out in the heats of the steeplechase. He took part in the 2009 IAAF World Half Marathon Championships in Birmingham and was 26th. He closed the year with a 29th-place finish at the 2009 European Cross Country Championships.