Clifford Chance (CC) has won a trophy mandate to advise on the £250m construction of the main London 2012 Olympic stadium.

The high-profile instruction will see CC advise the Olympic Delivery Authority (ODA) – the body responsible for overseeing the infrastructure for the 2012 London Olympics – on the building and procurement of the flagship stadium on the 500-acre Stratford site. The CC team is being led by construction partner Tim Steadman.

The news ends speculation over which firm would land the coveted contract after the ODA unveiled its five-firm panel last month. Along with CC, Berwin Leighton Paisner, DLA Piper Rudnick Gray Cary, Freshfields Bruckhaus Deringer and Pinsent Masons are all on the ODA's approved roster.

Construction of the 80,000-seat stadium is due to start next year and is expected to be completed within four years. The tender for contractors to design and construct the stadium was opened this week. The ODA is also responsible for future work, which will see the stadium used for other purposes once the Olympics are over.

It remains unclear whether CC won the mandate through its panel place or an additional tender. When the London Organising Committee of the Olympic Games (LOCOG) chose its legal advisers the body shelved plans to initiate a formal tender process and opted to appoint its existing advisers to advise on its mainstream work.

CC has been involved in the 2012 Olympics from the start, as adviser to the Olympic bid committee.