The railway currently has only 60 active volunteers out of a total membership of 750, and with plans to extend the line into Princes Risborough Train Station, help is needed more than ever.

On the open day a wide-ranging insight will be given into how the railway operates, including a look at the signal box currently under restoration, meeting the team who maintain the carriages and even learning how seven miles of line-side vegetation is maintained.

Marketing manager Andrew Bunyard said: "Not many people know how a railway operates and we decided an open day would give a better insight into what goes on. We are at the stage where we have just enough volunteers, but looking into the future we need more and younger people. We want them not just to visit, but to get involved in preserving the railway."

Currently, vintage trains leave Chinnor and get as far as the Thame Junction near Horsenden Lane in Risborough, but then have to turn back again. If plans get the green light, the locomotives would proceed into Princes Risborough Train Station, utilising the other side of the Birmingham bound platform.

The section of track they would run on was used by coal trains delivering to Chinnor cement works until 1989.

Mr Bunyard said negotiations with Network Rail were progressing, but at a slow pace.

"We are close but no deal has yet been struck. We are hoping that in next few months we can make an announcement that it has all been sewn up. It is obviously a major thing to get that last half-mile; it would give us a lot of momentum."