Travellers to Heathrow airport will reportedly face some 20 months of disruption while a new underground train link is built for the hub’s fifth terminal.

According to The Guardian, the airports group BAA has agreed to finance the £200 million project in return for a share of revenues on the line over the next three decades.

The newspaper states that, from January, tube services around the Heathrow “loop” will be terminated – and while underground trains will still service terminals one, two and three, anyone heading for terminal four will have to catch a bus from Hatton Cross underground station.

The information reportedly comes from “internal documents disclosed by Transport for London”. The newspaper suggests that the travel difficulties are likely to upset many airlines as well as travellers; many carriers have complained that they are in effect financing a terminal that will be used, in the most part, by British Airways.

The Guardian also provides a brief update on the new terminal’s progress; it is reportedly a third of the way towards being completed, with one of two tube tunnels having been completed and another currently being bored out.