Grosvenor was the third son of Grosvenor and Christina Lewin of Delungra NSW. At the age of nineteen he enlisted at Inverell in September 1915, having served two and a half years with the Senior Cadets. He had also been a member of the Little Plain Rifle Club. With two other volunteers who were on final leave, he was given a ‘Send Off’ at Delungra School of Arts Hall and presented with ‘souvenirs’.
He departed Australia for Egypt with the 1st Light Horse Regiment, 13th Reinforcement on HMAT A60 Aeneas in December 1915 and was subsequently transferred to the 5th Cyclists at Ferry Post. During June 1916 Grosvenor was sent to France. By the end of the year he was sick in hospital with influenza and did not return to his unit until early January. The following year he was transferred to the Australian Corps Cyclists Battalion.
Grosvenor returned to Australia in May 1919 and, with ten other returned men, was given a ‘Welcome Home’ at Delungra in August. He died in Sydney in 1981.
Grosvenor Lewin’s name is inscribed on the Inverell Honor Roll.