Consultancy firm Expedition have developed their proposals for a high speed rail link between Heathrow and Gatwick.
HS4Air is a proposed strategic high-speed rail/air connection that links the existing HS1 line with the planned HS2 line passing via both Gatwick and Heathrow airports to the south and west of London.
Expedition say their proposal, originally made earlier in 2018, offers benefits including fast direct rail access to both airports from cities north and west of London, direct high-speed train services from Manchester and Birmingham to Europe, with a 15-minute transfer time between Gatwick and Heathrow allowing them to share operations.
The line would run with the M25 or pass through tunnels under sensitive rural environments such as the North Downs.
The proposals are not currently funded.