Sir Gilbert Roberts studied civil engineering at Imperial College, graduating with a first in 1922. He was remembered by his college contemporaries as a brilliant raconteur, mimic, and a gifted mathematician.
After university he joined Sir Douglas Fox & Partners (later Freeman Fox), and worked on the complex calculations for the erection stages of the Newcastle and Sydney Harbour Bridges under Sir Ralph Freeman Snr. He then joined Dorman Long where he pioneered the use of all-welded steel joints, used for first time in Britain on Billingham Bridge, near Middlesbrough, in the early 1930s.
When Dorman Long went into receivership in 1934, Roberts joined Sir William Arrol & Co and was given the responsibility of developing designs in prefabricated welded steel plate and box girder sections for power stations, pipe bridges, gantry cranes, radio masts and the 400ton Goliath travelling crane.
His finest hour was during the 1950s when Ralph Freeman persuaded Roberts to leave Arrol - where he was a director - to take charge of the Severn Bridge superstructure design, assisted by Bill Brown and Mike Parsons. In his paper on the design of the Severn Bridge, given to the ICE in October 1968, Roberts described the step by step development of its revolutionary concept - the slender yet stable aerodynamic stiffened box girder bridge deck, the lightweight hollow box sections of the main towers and damping created by the inclined hanger arrangement. He took out a patent for the Severn Bridge design to protect his and Freeman Fox's interests. Roberts was also partner in charge of the Wye, Maidenhead and Bosporus bridges.
The end of his life was sadly marred by the collapse of the Yarra Bridge in Melbourne, a disaster for which he felt personally responsible.