27(1)Work is done where it is actually done, regardless of where the employment is held or the trade is carried on by P.U.K.
(2)But work done by way of or in the course of travelling to or from the UK by air or sea or via a tunnel under the sea is assumed to be done overseas even during the part of the journey in or over the UK.
(3)For these purposes, travelling to or from the UK is taken to—
(a)begin when P boards the aircraft, ship or train that is bound for a destination in the UK or (as the case may be) overseas, and
(b)end when P disembarks from that aircraft, ship or train.
(4)This paragraph is subject to express provisions in this Schedule about the location of work done by people with relevant jobs on board vehicles, aircraft or ships.