David Cameron and Boris Johnson delve into Crossrail tunnels David Cameron and Boris Johnson ventured deep underground to inspect Crossrail tunnels beneath London as the £15bn project construction project reached its half way mark. Joined by Stephen Hammond, the Transport Minister, the Prime Minister and the Mayor of London inspected work under way 25m beneath Tottenham Court Road, which will form one of several interchanges with London Underground when Crossrail trains begin running through central London in 2018. With the capital's population set to grow from 8.4 million today to 10 million by 2030, Crossrail is designed to relieve the pressure on its transport networks which are already overburdened. The project will increase rail capacity in London by 10 per cent, serving 38 stations and providing direct connections to Maidenhead, Heathrow, Shenfield and Abbey Wood. Mr Cameron said: "Big infrastructure projects like Crossrail are vital for the economy of London and the rest of Britain. They are the foundation-stone on which business can grow, compete and support jobs - a massive 55,000 jobs in the construction phase of this project alone. Western tunnels are due to be completed in the coming months, while major tunnelling beneath London should finish by the end of this year. Trains will be tested and delivered in 2017, and the tunnels will open to passengers in late 2018 under the current timetable. Mr Johnson said: "There was a time when some said that building a huge tunnel deep below the streets of London was a mad plan that would do nothing for our economy. But as this awe-inspiring project hits its halfway point - we can see how wrong the naysayers were. Crossrail will revolutionise east-west transit in the capital, making London an even more attractive place to visit and invest.