Heathrow third runway to force M25 redevelopment costing billions for rerouting

Heathrow’s chief executive, Thomas Woldbye, has revealed that the construction of the proposed third runway will require a significant re-routing of the M25, one of the busiest motorways in Europe. The existing 12-lane stretch of road, located between junctions 14 and 15, is set to be diverted through a new tunnel to accommodate the expansion.

The alteration to the M25 will pose considerable challenges for drivers, with the section currently handling an average of 200,000 vehicles daily. The airport’s plans outline that the motorway will remain operational while a replacement route, located 150 metres to the west and lowered by 4.5 metres, is constructed. Although maintaining traffic flow is a priority, extensive roadworks often cause disruption, heightening concerns about potential delays and closures during the process.

The government’s airports national policy statement mandates the construction of a full-length 3,500-metre runway at Heathrow, solidifying the need for these changes to the M25. While speculation earlier this year suggested a shorter runway might eliminate the necessity of motorway diversions, the latest confirmation ensures the longer runway remains central to the project.

Criticism from airlines using Heathrow has also emerged alongside expansion plans. Carriers including British Airways and Virgin Atlantic have voiced objections to the rising operational costs at the airport. Some have argued that increased landing fees, necessary to finance the expansion, would unfairly burden them. British Airways’ owner, IAG, previously accused Heathrow of squeezing its clients with high charges.

Woldbye, however, was quick to counter these claims. He emphasised the significant financial value Heathrow provides to both society and airlines, citing the robust demand for take-off and landing slots. Heathrow’s slots remain some of the most sought-after globally, with airlines trading them for substantial figures. For example, Oman Air paid $75 million for a pair of landing slots in 2016, demonstrating their market value.

Another challenge confronting Heathrow’s future is a steep increase in business rates. The airport is already the highest business rates payer in the UK and is set to face a 50 per cent rise from April 2026. The rates, projected to total over £300 million annually, bring the overall three-year figure close to £1 billion, placing additional financial pressure on Heathrow management as they navigate both the expansion and ongoing operational costs.

The expansion proposal, which includes the third runway and its impact on regional infrastructure, continues to divide opinion. While it aims to meet growing airport capacity demands, its associated costs, logistical complexities, and environmental implications will likely remain subjects of debate in the coming years.