Very few remnants of this Norman chapel are visible in the present day church, some surviving stones with a diaper pattern are built into the chancel.

The substantial money brought in from this royal grant enabled the Burgesses of Alnwick to turn St Michael's into "one of the finest examples of the perpendicular style of architecture in the north".

[3] There were no further changes to the church until the latter years of the 18th century when Hugh Percy, 1st Duke of Northumberland, after renovating Alnwick Castle, repaired the chancel using his own architect Vincent Shepherd (1750–1812) assisted by Italian craftsmen.

The work included a new window in the middle of the east end, a fan vaulted plaster ceiling and oak stalls for the Duke and his family.

Funds for this project came from a large donation from Hugh Percy, 3rd Duke of Northumberland, and from money raised through the church rates and the sale of seats.

[6] At the south-east corner of the building is a hexagonal turret which originally gave access, via a spiral staircase, to a four-storey roof chamber, fifteen by thirteen feet wide.

Below the west window is the modern font, made from Kilkenny blue-black limestone by David Edwick of Hexham as a gift for the new millennium.

The chapel has an interesting pillar featuring the Percy and de Vesci arms and a carving of St Catherine and the wheel on which she was martyred.