The east window is a striking feature of the interior of the church.
It is in the form of a tree.
The window is a memorial to Isabella, Lady Ewart, the wife of Sir William, a wealthy linen magnate, who was one of the founders of St Mark's Church.
The nave, aisles and tower were built in 1878 and the chancel and transepts were added in 1891 at the expense of the Ewart family, as a memorial to Sir William.
On the south wall of the sanctuary is the tablet which records his life and Christian service.
His son, Sir William Quartus Ewart, is remembered in the window of the side chapel in the south transept.
