FATHER and son architects John and Benjamin Green didn’t do ordinary as they crafted what would become Tyneside landmarks.

Their efforts in Newcastle included Grey’s Monument, the Theatre Royal – and the 918ft long 1839 Ouseburn Viaduct which now carries the main East Coast railway line.

Now Network Rail engineers are tackling the £10m challenge of giving the Grade II-star listed bridge a new lease of life.

Dave Lugsden, Network Rail programme engineering manager for the North East and Scotland, yesterday said: “It is a superb historical structure but it is a difficult job as it is one of the most complex structures on the UK railway network.”

The bridge is currently being cocooned in scaffolding for a job which will last until the end of March next year.

The Ouseburn viaduct, and its twin bridge, at Willington Quay, North Tyneside, were originally built between 1837-39 in the new material of laminated timber.

This was replaced in 1869 with an exact copy of the complicated structure but in wrought iron, while keeping the original stone approaches and piers.

The rail deck of the Newcastle viaduct, which has five main arches, is 108ft above the River Ouseburn.

Engineers have been studying the structure for the last 10 years to understand its complexities.

A 20mph speed limit has been in place on the bridge for the last two years but this will be lifted when the strengthening work is complete.

Mr Lugsden said that because some parts of the bridge were included for their visual effect, one of the aims of the £100,000 research work project was to determine exactly which elements of the structure actually bear weight.

He said: “Some of the wrought iron made 140 years ago, is of variable quality, depending on where it was produced, and it can vary quite a lot terms of the stresses it can take.”

Steel plates and bolts will be used in the strengthening operation, with virtually all of the new material carefully concealed behind the wrought iron parts.

The engineering works will be good for at least another 50 to 60 years, and the bridge will also be repainted.

Samples of previous paint coats have been taken and the colour has yet to be decided but could well be grey.

Network Rail area general manager Warrick Dent said: “This is the first significant investment in this viaduct in many years and will allow us to deliver safe, reliable services for passengers for many years to come.”

This is a significant investment and will allow us to deliver safe, reliable services for passengers for many years to come