Engineers working on repairing Ireland Bridge in Bingley have uncovered several 17th century masons’ markings.

For the first time in centuries, workers can see the bridge as it was when it was originally built in the 1600s, before it was extended in later years.

The bridge was closed to traffic in January for six months as essential strengthening work is taking place.

Work on the Grade II-listed structure was due to start last July, but the discovery in the arches of a roosting colony of rare Daubenton’s bats caused a deal in which a new home for them was found.

Mark Brundle, Bradford Council’s senior highways structures engineer, said several 17th century masons’ markings had been found on the historic bridge.

He said: “We are repointing areas of the bridge and have scaffolded it out. This has enabled us to see the whole of the bridge – it’s the first time in centuries that anyone has seen it in such detail as it was when first built in the 1600s, before it was extended in 1700.

“The craftsmen’s marks were personal to them, one of them is a symbol of an eye with a line across.”

John Anderson, Bradford Council’s principal highways structures engineer, said investigations had revealed the bridge, built in 1685, had been in a very poor condition prior to its closure.

He said: “The structure had deteriorated to such a condition that it would have had to be closed to traffic this year on safety grounds.”

Bradford Council is taking advantage of the road closure to rebuild retaining walls and replace old street lights in Harden Road.

A new footpath connecting the bridge with the St Ives Estate will also be laid. Work on the bridge is due to be completed in July.

While the work is going on, Council officials have agreed to consider introducing changes to car parking charges in Bingley, following consultations with traders in the town.

The changes, aimed to benefit shoppers and local businesses, are designed to offset any negative effects for trade caused by the road closure while the work is carried out, said a Council spokesman.