By 1836 the old parish church of St Laurence, Upton was falling into disrepair. It was felt that a new church was needed to replace it. The foundation stone for the new church was laid that same year by the Duke of Cambridge.
In July 1837 the new church was consecrated with the name of St Laurence. Until July 1850 marriages carried out at the church were not considered legal as the necessary paperwork had not been completed properly. A new Act of Parliament was passed to rectify the situation!
By the 1860s the population of Slough had increased. It was decided to enlarge the existing building, rather than build a new church. A design by John Oldrid Scott was chosen. Queen Victoria herself made a contribution to the building fund. In 1878 the chancel, transepts and one bay of the nave were completed and consecrated.
As the old parish church of St Laurence had been renovated rather than demolished, there were now two churches with this name. The name of the new church was therefore changed to St Mary's. In 1912 the nave was completed by a local builder, Mr H D Bowyer. Other enhancements such as an organ and electric lighting were then added.
James Elliman, a local businessman, provided much of the money. His generosity allowed for the tower and spire to be constructed - also by Mr Bowyer. On 2nd April 1913 a flag flew on top of the spire to celebrate the laying of the last stone. A few days later the churchwarden, Mr Parker, placed an arrow on the weather vane that was mounted on top of the spire. Before Mr Parker made his ascent, James Elliman was taken up by the builder to inspect the spire.
The tower, spire and newly installed bells were dedicated by the Bishop of Stepney on 19th June 1913. The spire that still features so prominently on Slough's skyline is thought to be the last one in the country to have been built of stone.