The first successful rectangular tunnelling shield was developed by Marc Isambard Brunel and patented by him and Lord Cochrane in January 1818. Brunel and his son Isambard Kingdom Brunel used it to excavate the Thames Tunnel beginning in 1825 (though the tunnel was not opened until 1843). Brunel is said to have been inspired in his design by the shell of the shipworm, a mollusc whose efficiency at boring through submerged timber he observed while working in a shipyard. The shield was built by Maudslay, Sons & Field of Lambeth, London, who also built the steam pumps for de-watering the tunnel.