Complex sentence: Hugh O'Donnell was appointed chief executive in 2000 and the company was subsequently listed on the Alternative Investment Market in February 2008 and transferred to the main market of the London Stock Exchange in July 2011.
Split into simpler sentences: Hugh O'Donnell was appointed chief executive in 2000 and the company was subsequently listed on the Alternative Investment Market in February 2008. Kentz was transferred to the main market of the London Stock Exchange in July 2011.