Jim Al-Khalili talks to Robert Mair, professor of Civil engineering at Cambridge University about his life as an engineer in academia and industry and his expertise on finding innovative solutions to the problems of building tunnels under already congested cities.

He talks about his innovative technique of 'compensation grouting' which prevented Big Ben from tilting and even cracking and coming away from the Houses of Parliament during Jubilee line extension.
Crossrail is one of the biggest engineering projects in Europe and involves constructing 26 miles of new tunnels underneath London's busy streets and under the existing tube network. Robert talks the latest tunnelling technology being used and the huge drilling machines with names like 'Ada' and Phyliss' which use high pressure to minimise ground movements as they drill and even have a kitchen and bathroom facilities on board.
He also talks about his latest work on how smart sensors which can harvest their own energy. And when built into buildings, roads, tunnels they could make sure the engineering projects of the future will be able to continuously monitor and report on their own safety.