May 2021 - Project under planning stage; April 2021 - Private companies will be invited this summer to fund, finance and build the project; January 2018 - Project has received investment from Aecom; August 2017 - Plans have been unveiled for project which aims to link Heathrow Airport with trains from Guildford, Farnborough, Working and London Waterloo; Project cost - GBP1.3bn