Construction of St Albans Cathedral’s new visitor centre, to boost knowledge of Britain’s first martyr Alban, is a step closer after the start of an archaeological dig.

Over the past fortnight, experts from the Canterbury Archaeological Trust have been up to their knees delving in 50cm-deep trenches in Sumpter Yard, next to the Slype entrance of the historic landmark.

They have been excavating to discover as much as possible about what lies in the ground, to ensure that the archaeology is not damaged or disturbed by construction of the new Welcome Centre, and that the building will have solid foundations.

The multi-million-pound Heritage Lottery Fund project aims to broaden knowledge of the story of Alban and, in conjunction with the new St Albans museum project incorporating the Town Hall, to increase visitor numbers to the city and the iconic church.

It is hoped that the trust’s experts will have a glimpse into the site’s medieval past.

Cathedral archaeologist, Prof Martin Biddle, said that a self-seeded yew tree had been cut down in preparation for the exploratory work in what is known as ‘the Monk’s Graveyard’.

He said: “The trust has dug a series of trenches very carefully to tell us as much as possible about what lies there.”

While the cathedral has a ‘pretty good idea’ there were previously two apses projecting from the east side of the south transept, they were demolished, probably in the 13th century.

The cathedral is keen to find out about a large rectangular building in the angle between the transept and the presbytery, of the later 13th or 14th century that “we know nothing about”, Prof Biddle said.

Other buildings in the angle were removed after the Dissolution of the abbey in 1539, and for the next three centuries, until about 1852, the area served as the parish graveyard.

Prof Biddle added: “Some of the grave slabs can still be seen. The graves will be disturbed as little as possible.”

The Herts Advertiser understands that the project will go out to tender shortly, with construction of the Welcome Centre expected to begin in Spring.

The dig itself is expected to finish tomorrow (Friday).