Thousands of rail enthusiasts are expected to line the tracks as a majestic visitor steams into the platform for a heritage railway's biggest-ever gala event this weekend.

The star attraction of the Mid Norfolk Railway's Summer Steam Gala will be the 1938-built Duchess of Sutherland, an example of Britain's most powerful passenger locomotive which used to haul express services between London and Glasgow.

It is one representative from the 'Big Four' of railway companies gathered together for the event, running from today to Sunday, which organisers hope could bring much-needed income towards the railway's future ambitions.

After opening its latest northward track extension to Hoe in May, the MNR Preservation Trust has secured planning permission to put up a salvaged Victorian footbridge which will link two of its platforms together at Dereham Station.

That project will open up the station to improved services and give access to a longer-term 'East Side Vision' of creating a museum and visitor centre in the former goods shed and stable blocks.

Meanwhile, the major fund-raising focus is for a £90,000 new maintenance shed, which would allow year-round engineering work, out-of-season educational visits and increase the appeal for visiting locomotive owners. The MNR's volunteer managers hope these developments will combine to boost the line's tourism appeal and heritage reputation – but first, it needs to secure grant funding and donations, through events such as this weekend's event.

MNR member and former chairman Roland Terry said: 'This gala is really about showcasing us. We are moving up the leagues but a lot of the 'Premier League' heritage lines like the North Yorkshire Moors have been in the business a lot longer than us.

'Our main thrust at the moment is to raise funds for the maintenance shed. At the moment our maintenance has to be done in all weathers. We have always been hampered by this lack of covered accommodation. It would put our name even more on the map and could be the foundation for even bigger events in the future.'

The gala's star attraction will be the 1938-built Duchess of Sutherland, an example of Britain's most powerful passenger locomotive which used to haul express services between London and Glasgow.

Alongside a full schedule of departures during the weekend a dining train, serving a four-course meal on the Duchess of Sutherland will run on Saturday, while there are also opportunities for footplate rides on the famous engine.

John Hull, vice chairman of the MNR, said while ticket sales from the steam gala would cover the costs of the event, any additional donations would go towards the longer-term projects.

'We are on the cusp of moving into the really big time,' he said. 'These special events are all big money earners which will help us build for the future.

'We cannot use that other platform until we have a footbridge, so that's the only way we can get full use of the station. It is essential to our East Side Vision because we could link it to the development of the goods shed as a museum and exhibition centre.'

The replacement footbridge at Dereham station was salvaged from Wittlesford, Cambridgeshire, where it was dismantled in 1965. Once restored and re-built, it will be painted in the British Railways standard colours of green and cream.

The estimated cost of the project is around £30-50,000, and it is hoped that funding could be in place to begin construction next autumn.

The MNR Preservation Trust, established in 1995, owns 17.5 miles of track and track-bed, including the disused section north of Dereham as far as County School station – the next destination on its extension plans.

The renovation of the track is key to the long-term goal of reconnecting its market town base with its northern neighbour in Fakenham.

Operations director James Steward, whose day job is as an area customer service manager for Greater Anglia trains, said the MNR was keen to recruit more people to join a 100-strong army of volunteers.

'It is crucial,' he said. 'The main things for us at the moment are trying to attract more volunteers and having better covered facilities.

'A lot of other heritage railways have been there an awful long time, and we are in the first phases of growing. But we are starting to mature. It is a very exciting time where we can start to show the people what our ideas are for the future, and our vision for how we achieve that.'

For full steam gala information and timetables, see www.mnr.org.uk/calendar/events/steamgala. To enquire about volunteering, call 01362 851723.