The Alvis TC 108G was a British sporting car made by Alvis cars between 1955 and 1958. Coachbuilders Graber of Switzerland had produced some bodies for the TC21 that were much more up to date than the standard offering from Mulliners. Mulliners was increasingly coming under the control of Standard Triumph, they were purchased by them in 1958, and the body supply had been getting difficult. Alvis's other main supplier was Tickford and they were bought by David Brown to use for his Aston Martin company. It was therefore decided to make the Graber style the basis of a new model and the rights were bought resulting in the TC 108G.
A contract was placed with bus builder Willowbrook of Loughborough. The car was only available as a two door, four seat saloon made by forming metal around a traditional wooden frame. This proved to be expensive and the deal was terminated and a new contract placed with Park Ward, the modified vehicle becoming the TD21.
The 2993 cc engine was uprated slightly to produce 104 bhp (78 kW) at 4000 rpm by modifying the cylinder head and fitting twin SU carburettors. Suspension was the same as the TC 21, independent at the front using coil springs with leaf springs at the rear.
In total only 37 cars were made, including several on chassis supplied to coachbuilders other than Willowbrook.