The man behind consultant engineer Arup's work on the Eurotunnel, the 2012 Olympic bid and Crossrail will leave his role as director in April.
Mark Bostock, who has been with Arup for nearly quarter of a century, will step down after reaching the company's retirement age, but will continue to work as a consultant for three to four days a week.

Bostock currently sits just below main board level and is on the infrastructure board. He said: "I joined the firm in 1980 to set up Arup's economic consultancy, but I've now hit the retirement age of 65. It feels rather remarkable."

In the consultancy role Bostock will largely focus on Arup's alternative to the east-west London railway Crossrail, known as the London Regional Metro. This alternative would involve digging a tunnel underneath London to link the Great Eastern and Great Western rail lines. At a proposed cost of £3.26bn, it would be several times cheaper than the official Crossrail proposals.

Bostock said: "This is a very simple proposal, a no-brainer really. It would be financed by the private sector, but need to be underwritten by the government." The private sector funding is largely in place through Arup's consortium partner Bank of Scotland.

Arguably Bostock's greatest achievement was the success of Arup's proposal to reroute the Channel Tunnel Rail Link. Bostock challenged the initial plans for the route, and said that it should enter London from the east through the Thames Gateway. This idea was accepted by the government in October 1991.

Bostock also headed up Arup's cost-benefit analysis of the London bid to host the 2012 Olympics. This report has since formed the basis of the capital's bid, and included potential sites such as the main stadium and Olympic village being built in Stratford, east London.

Bostock is also a member of the Royal Institute of International Affairs and CBI London Regional council committees.