Signage is seen at the UK border control point at the arrivals area of Heathrow Airport, London, September 3, 2018. Picture taken on September 3. REUTERS/Toby Melville

LONDON (Reuters) - Britain will outline its post-Brexit immigration policy next week, House of Commons leader Andrea Leadsom said on Thursday, confirming the publication of a long-awaited paper on one of the government’s central policies.