Heathrow Airport Limited appointed Grimshaw as concept architect for its expansion masterplan, covering new terminals, satellite concourses, aprons and passenger interchange. Working alongside Arup, Mace, CH2M & Turner & Townsend and other specialists, Grimshaw developed a vision for the proposed 3,500-metre third runway and a new terminal planned for 35 million passengers a year. The £16 billion proposal aimed to increase airport capacity from 480,000 to 740,000 aircraft movements annually. The design had to accommodate major changes to the M25 while addressing passenger experience, environmental impacts and the needs of neighbouring communities.