The British Transport Police (BTP) (Welsh: Heddlu Trafnidiaeth Prydeinig) is a special police force that polices railways and light-rail systems in Great Britain, for which it has entered into an agreement to provide such services. 95% of the Force's funding comes from Britain's privatised train companies. British Transport Police officers do not have jurisdiction in Northern Ireland unless working under mutual aid arrangements for the Police Service of Northern Ireland in which case any duties performed on a railway will be merely incidental to working as a constable in Northern Ireland.