Holding answer received on 25 June 2018
Network Rail are funded by the Department for Transport to submit the Development Consent Order for the Western Rail Link to Heathrow. The 2013 Aviation Policy Framework clearly sets out that developers should pay the costs of upgrading or enhancing road, rail or other transport networks or services where there is a need to cope with additional passengers travelling to and from expanded or growing airports.
The Western Rail Link to Heathrow has a wider range of beneficiaries, and the Government will consider, along with other relevant stakeholders, the need for additional public funding. The quantification of non-airport benefit is dependent on agreement of the final design and decisions on the train operating company. This is expected in Summer 2019. The airport contribution would be subject to a negotiation, and review by regulators.