IRV is currently used in the United Kingdom for by-elections to the Northern Ireland Assembly and to local assemblies in Scotland, both of which use the single transferable vote method of proportional representation in regularly scheduled elections. It is used in its contingent vote form (also called the supplementary vote), for all direct elections for mayor in England, including in London. It is used to fill vacancies within the House of Lords, to elect the leaders of the Liberal Democrats and the Labour Party and for many private elections, including for Chancellor of Oxford University and rectorial elections at the University of Edinburgh. IRV was the electoral method available to select a replacement MEP by election for the Northern Ireland constituency of the European parliament, however now a party can co-opt a replacement without the need for a by-election.