The new government rules with the support of the right-wing Progress Party - which wants repatriation of refugees and immigration quotas.

BBC: Portugal continues centre-right trend

There followed a huge campaign to change party rules, and replace former Callaghan supporters with left wing members who would oppose the Common Market, and support a policy of state ownership.

BBC: The Michael Foot story

New rules have forced modifications which lower and widen the front wing, and demand a tall, narrow rear wing.

BBC: Hamilton eyeing second title bid