These trains currently offer high-speed services between London St Pancras and Kent.
Expected to take seven months, the project’s initial phase will consist of design, engineering, and procurement.
In March next year, upgrades to the first of the 29 trains will begin at Southeastern’s Ashford Depot.
The programme will cover the refurbishment of the complete interior, including new carpets and seats, as well as new seating layouts for people with reduced mobility.
It will also include a live passenger information system (PIS) upgrade, including media screens, from 2024 besides a CCTV system upgrade.
Other upgrades include USB at-seat charging and LED lighting deployment.
The installation of the latest digital solutions in the trains is expected to facilitate efficient passenger management and infrastructure monitoring.
Eversholt Rail will deploy new CCTV, which combined with Hitachi Rail’s digital tools, will offer live passenger data on numbers and load weighting.
The Javelin fleet is anticipated to become one of the first in the UK to implement Hitachi Rail’s digital infrastructure monitoring technology.
Exterior roof-mounted high-definition cameras will help deliver live monitoring of overhead lines and surrounding equipment.
Eversholt Rail client services director Paul Sutherland said: “We are delighted to be working in partnership with Southeastern and Hitachi Rail to deliver these upgrades to our Class 395 fleet.
“Our investment in this package of upgrades will ensure these high specification trains continue to provide the passengers on HS1 with a superior service.”