The electric and diesel powered trains, financed by Eversholt Rail Group, will deliver faster more frequent services and additional seats for customers travelling on the Great Western Main Line.
These Inter City trains are in addition to the 57 trains Hitachi is delivering to GWR as part of the UK government's Intercity Express Programme (IEP) from next year, and follow on from the 29 trains ordered in 2015.
Karen Boswell, Managing Director of Hitachi Rail Europe, commented on the deal announcement:
"Hitachi is pleased GWR and Eversholt Rail Group have exercised one of the options they have with us to increase their fleet. This further strengthens our working relationship with two major customers. It is a further endorsement of our current work delivering modern, high-speed modern trains, connecting people and communities across the GWR network.
"The iconic image of this brand new, high-speed fleet operating on a railway rich in heritage will be another landmark moment for Hitachi and one we are delighted to make a reality."
The Addleshaw Goddard rail team supporting Hitachi was led by Paul Hirst, Head of Transport.