Sir Marc Isambard Brunel, FRS FRSE (25 April 1769 – 12 December 1849) was a French-born engineer who settled in England. He preferred the name Isambard, but is generally known to history as Marc to avoid confusion with his more famous son Isambard Kingdom Brunel. His most famous achievement was the construction of the Thames Tunnel.
The Thames Tunnel is an underwater tunnel, built beneath the River Thames in London, connecting Rotherhithe and Wapping. It measures 35 feet (11 m) wide by 20 feet (6 m) high and is 1,300 feet (396 m) long, running at a depth of 75 feet (23 m) below the river surface measured at high tide. It was the first tunnel known to have been constructed successfully underneath a navigable river,and was built between 1825 and 1843 using Thomas Cochrane and Marc Isambard Brunel's newly invented tunnelling shield technology, by him and his son Isambard Kingdom Brunel.The tunnel was originally designed for, but never used by, horse-drawn carriages. It now forms part of the London Overground railway network.