Clients including P&O and the United Nations use Pole Star’s Purplefinder satellite technology to track ships, trucks and aircraft around the world. The London company, launched by Darrel Sheinman and led by chief executive David Plumer, also makes security alert systems that ships are required to fit as a defence against hijacking. This year a private investor bought a 24% stake in the business for a reported £3m. Overseas expansion has helped boost sales 63% a year from £1.8m in 2003 to £4.7m in 2005.