The son of William Austyn Mair, Francis Mond Professor of Aeronautical Engineering at the University of Cambridge (1952–1983), Mair was educated at St Faith's^[9] and The Leys School in Cambridge and went on to study Engineering at Clare College, Cambridge, gaining a MA degree in 1975^[10] and a PhD degree in 1979.^[11]

Lord Mair is an authority on geotechnical engineering,^[12] which is the application of the science of soil and rock mechanics, engineering geology and other related disciplines to civil engineering design and construction. His particular speciality is the design and construction of tunnels. His expertise has been sought throughout the world on numerous civil engineering projects involving soft ground tunnelling, retaining structures, deep excavations and foundations.

Prior to his appointment to a Chair at Cambridge in 1998, he worked in industry for 27 years. He was Principal Engineer for Scott Wilson Kirkpatrick, working in their London and Hong Kong offices, 1971–1983; he was seconded to the University of Cambridge, 1976–1979 to research tunnelling in soft ground.^[13]

In 1983 he founded the Geotechnical Consulting Group, an international consulting company based in London, with co-founders Dr David Hight and the late Professor Peter Vaughan. He has been responsible for advising on geotechnical and tunnelling aspects of numerous major engineering projects world-wide. In the UK he advised on the design and construction of the Jubilee Line Extension for London Underground, the Channel Tunnel Rail Link (now HS1), Crossrail^[14] and HS2 projects. He is known for introducing compensation grouting as a novel technique for controlling settlement of structures during tunnel construction on the Waterloo Escalator Tunnel Project. He successfully used the technique on the Jubilee Line Extension project for the protection of many historic buildings, including the Big Ben clock tower at the Palace of Westminster.^[15] Compensation grouting is now widely used around the world. International projects on which he has advised have included railway and metro tunnels in Amsterdam, Athens, Barcelona, Bologna, Florence, Hong Kong, Istanbul, Rome, Singapore and Warsaw, and motorway tunnels in Bolu, Turkey. He was a member of the French Government Commission of Enquiry into the Collapse of the Toulon Tunnel, 1997. From 2007 to 2014 he was Co-Chairman of the Singapore Government's International Advisory Board on design and construction aspects of all its underground metro and road tunnels.

Lord Mair was a member of Crossrail's Engineering Expert Panel^[16] and is a member of the Expert Technical Panel of the National Infrastructure Commission.^[17] He was Chairman of the Royal Society/Royal Academy of Engineering Report on Review of Shale Gas and Hydraulic Fracturing, published in 2012.^[18]

Persuaded to return to academia in 1998, when appointed to a Chair in Engineering at the University of Cambridge, he championed industry-focused research and grew the Geotechnical and Environmental Research Group into one of the largest in its field in the world. He was the Sir Kirby Laing Professor of Civil Engineering 2011-2017 and was Head of Civil Engineering 1999–2016.^[19]

Mair organised the successful £2m bid for a Joint Infrastructure Award for the construction and equipping of the Centre for Geotechnical Process and Construction Modelling adjacent to the centrifuge facility on the West Cambridge site, which is part of the Schofield Centre.

He led the establishment in 2010 of the Laing O'Rourke Centre for Construction Engineering and Technology at Cambridge, a partnership between the University of Cambridge and Laing O’Rourke – the UK's largest private construction company – to set up a multi-disciplinary academic centre to leverage innovative thinking to benefit the construction industry.

Lord Mair is Head of the Centre for Smart Infrastructure and Construction (CSIC) at the University of Cambridge,^[20] an Innovation and Knowledge Centre funded by the Engineering and Physical Sciences Research Council (EPSRC) and Innovate UK and industry to a total value of £22m. CSIC specialises in sensor technologies and data analysis models, working with industry and partner organisations to accelerate implementation of research outputs to transform infrastructure through smarter information. Its work involves developing new technologies for streamlining construction and for condition assessment and monitoring of ageing infrastructure, with a focus on the development of wireless sensor networks, MEMS technologies and new fibre optic sensing technology. CSIC has around 50 industry partners and has deployed innovative sensor technologies (notably fibre optics and wireless sensors) on around 100 different sites.^[21]

In 2015 he was responsible for securing £18m Government funding for 50 per cent of the cost of the new Civil Engineering Building on the West Cambridge site of the Engineering Department as part of the UK Collaboratorium on Research on Infrastructure and Cities (UKCRIC) initiative.^[22] The £38m building, which opened in 2019, contains the National Research Facility for Infrastructure Sensing (NRFIS).^[23]

In 2020, Mair was appointed chair of the board at One CAM, the company responsible for delivering the Cambridgeshire Autonomous Metro.^[24]

Mair was elected as a Fellow of the Institution of Civil Engineers (FICE) in 1990, a Fellow of the Royal Academy of Engineering (FREng) in 1992,^[25] and a Fellow of the Royal Society (FRS) in 2007.^[26] Mair delivered the 46th Rankine Lecture of the British Geotechnical Association in 2006, and was appointed Commander of the Order of the British Empire (CBE) in the 2010 New Year Honours.^[27] Mair has been awarded numerous research grants by the Engineering and Physical Sciences Research Council (EPSRC).^[28] He was awarded the Institution of Civil Engineers Gold Medal in 2004, their President's Medal in 2013 and their Crampton Prize in 2006 and 2015.^[29] He has given many invited lectures around the world, including the flagship annual Hinton Lecture of the Royal Academy of Engineering in 2015 titled 'Creating underground infrastructure – the role of geotechnical engineering'.^[30]

On 29 October 2015, he was created a life peer with the title Baron Mair, of Cambridge in the County of Cambridgeshire.^[31]

In February 2019, Mair was elected a foreign member of the US National Academy of Engineering for contributions to underground construction and smart infrastructure and for leadership in government, engineering practice, research, and education.^[32]

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