A six-year campaign has come to a successful close following the electrification announcement of the Barking to Gospel Oak Overground line on Thursday, but there are still questions to be answered.

Chief Secretary to the Treasury Danny Alexander said the line would receive around £115m in funding for electrification.

The Barking to Gospel Oak Rail User Group, who have been campaigning for more than half a decade, expressed gratitude to those who helped achieve the goal but also want clarification over the money’s allocation.

A group spokesman said: “It is still hard to believe that after six years campaigning, during which time it certainly felt we were banging our collective head against a brick wall, at least as far as Government were concerned, that the 10-mile ‘diesel island’ of the Barking to Gospel Oak line is finally being integrated with the rest of north-east London’s electric railway.”

“The surprising thing about today’s announcement is that the Government’s investment in the electrification is said to be £115m, way over the £45-50m estimated by the industry and campaigners.”

Questions remain over the money’s exact nature, including whether the figure encompasses a £25m commitment from Transport for London already made toward electrification, as well as whether the figure included funding for TfL to source electric rolling stock.

The spokesman added that passengers would benefit from quiet, pollution free electric trains with quicker acceleration and more coaches.

It should now be possible to progressively change freight trains crossing North London from diesel to electric locomotives, further reducing noise and pollution.

All trains on the line are currently diesel powered.

Caroline Pidgeon, Leader of the Liberal Democrat London Assembly Group, said: “This is incredibly welcome news.

“Electrification of this railway line is exactly what long suffering passengers on this line have been waiting for.

“They can now look forward to a much more reliable service.

“The Barking to Gospel Oak users group have done a great job over the years in helping to keep the pressure up on this issue and it has been a delight to have campaigned alongside them.”

The User Group offered its thanks to MPs Stella Creasy and John Cryer, among others, for their support.

The group spokesman said TfL are planning to start work in 2015 but that the group would be pushing for work to begin as early in next year as possible.