....but not until 2029.....
From the Heathrow Airport Limited response the the Davies committee:
Heathrow would also have the capacity to connect to a number of routes within the British Isles currently served by competing hub airports in Europe, for example: Guernsey, Jersey, Inverness, Isle of Man and Humberside. Connecting ten UK regional airports, with an average of three services each per day, and connecting 40 more long-haul destinations with a daily service requires 50k ATMs (Air Transport Movements) per annum. This represents about 20% of the full potential additional ATMs of a third runway. The remaining 80% of additional capacity would be used over time to improve connectivity via increased frequencies on existing long-haul routes and across the short-haul network.
Full submission here:
Long Term Capacity Options - HAL response
Of course history will repeat itself when that 80% excess capacity is used up and we'll be booted out, but I reckon I'll be long gone by then!