The Eurolink consortium, made up of Miller and French and Austrian partners, has won a pounds 110m order for tunnelling and a bridge across the Medway in Kent along the route of the 68-mile link.
The pounds 5.4bn link is being built in two stages. The first phase will end at Fawkham Junction in Kent where the link will then continue into Waterloo on existing lines.
The second phase, involving construction of the link into a dedicated terminal at St Pancras station, will be built largely in tunnels from Stratford in east London.
Miller is also bidding for the tunnelling work on the second phase of the link. Construction of the first phase is due to be complete by 2003 with the completed link opening in 2008.
News of the contract award came as Miller unveiled a 24 per cent increase in interim pre-tax profits to pounds 4.8m and indicated that a flotation was an option in the long term.
The group, which has interests spanning general construction, civil engineering, house-building, mining and property development, made pre-tax profits of pounds 13.5m last year. Chief executive Keith Miller anticipated a significant improvement this year.
A flotation could value the business at upward of pounds 200m.
Miller, founded in 1934, has become one of the biggest private-owned construction groups, with 2,200 employees and sales of pounds 323m. The shares are 100 per cent owned by the Miller family, with six principal shareholders.
The group has a forward order book of pounds 270m and is currently building the biggest sewer in Britain - a 7.5m storm water tunnel at Hastings.