Second-hand rolling stock will have to be used for a new rail service from the north-east of England to London for at least two years, bosses have said.
Grand Central will eventually have a new fleet of trains
Grand Central is to operate a three times a day service from Sunderland to London, taking in stations in Teesside and North Yorkshire.
The firm fought off a legal challenge from GNER to run the rival service on the East Coast Main Line.
But delivery problems have forced it into using alternative rolling stock.
Grand Central says it has purchased three 125mph high speed trains and plans to spend a total of £5m over the coming months.
Managing director Ian Yeowart said: "After many years of hard work we are naturally delighted that the securing of quality rolling stock means our services are guaranteed."
Mr Yeowart said 125mph trains would be used to launch the new service, with new 140mph trains expected to be drafted in by 2009.
When Grand Central initially announced plans to operate services in 2004 it was envisaged that surplus Class 222 trains would provide the rolling stock, but a series of continuing delays meant that option could not be taken - and they were leased elsewhere.
Ian Yeowart added: "Although this stock is seen as an interim solution, it is a fact that high speed trains are still regarded by many as the premier train on the network.
"The challenge will be to ensure that its replacement in a few years rekindles that iconic status."