 French nuclear power will fill a looming generation gap in Britain thanks to a new cross-Channel, (EURO)250 million interconnector being built by Eurotunnel.  The electricity cable will be installed in the service tunnel, enabling the link to be in place quicker and for less money than if the project had to be built from scratch.  The 75-kilometre interconnector will have a capacity of 500 megawatts, enough to power about five million homes. It is being built together with European investment fund, Star Capital Partners, which will hold a 51 per cent stake with the remainder owned by the operator of the Channel Tunnel. When it is operational by early 2015, it will boost capacity between the two countries by a quarter, enabling British-generated electricity to be exported to France when there is a surplus.  Jacques Gounon, Eurotunnel chief executive, said that energy experts had told the company that there could be shortage of supply in the UK between 2015-2017. More than 11 gigawatts of old coal plants will be shut down in 2015 because of new European environmental legislation, while the next wave of nuclear reactors will also begin to come offline shortly afterwards.  The Government is drawing up incentives to try to ensure that companies invest in new plant to plug the gap but many executives fear that it may not be built in time. Electricity supply will also become considerably more variable across Europe as the amount of intermittent renewables come online, requiring greater interconnectivity to make sure power is always on tap.  Mr Gounon said: "It's good for Eurotunnel to strengthen ties between France and the UK."  This month a new electricity interconnector linking the UK to the Netherlands was opened.  Mr Gounon added that the cables would be attached to the ceiling of the service tunnel and there would be no danger to train passengers in the event of an evacuation. The service tunnel is about 4.6 metres high.