As each rolling stock manufacturer works to finalise its bid ahead of the invitation to tender in spring 2018, we take a look at the companies' capability and capacity to build high-speed trains for one of Britain's most lucrative train contracts.
These upgrades are being funded from the state's 2018-19 budget and will be delivered in stages, with services coming online progressively from the early 2020s.
Balfour Beatty’s Mark Bullock, managing director of rail and utilities.

Review: Infrarail 2018

First staged in 1994, Infrarail is firmly established as Britain’s leading showcase for every aspect of railway infrastructure, technology and expertise, with a strong reputation for attracting visiting managers, engineers and buyers at the highest level.
Keller and Intrafor have already provided a "significant amount" of early technical advice to optimise design.
It will almost quadruple the current capacity from 12 trains per day to 46.
The Czech Republic's transport ministry has announced that Deutsche Bahn will design the Krušné Hory tunnel, a key project in the proposed €5 billion high-speed line between Prague and Dresden.
The stations are being built as part of the 9km twin-bore Melbourne Metro Tunnel, a major enhancement that promises to free up capacity on the capital's rail network.
National Infrastructure Commission chair Sir John Armitt said that firm decisions on the megaproject's timetable and funding should be made by the end of 2018.
Andrew is expected to take up his new role in early autumn following a period of handover with Mark Carne.
More than $1 billion has been put aside by the Australian government for Perth's Metronet suburban rail projects.