[6] It is laid out in a classic cruciform and comprises a nave, aisles, north and south transepts and the chancel which is surrounded by four guild chapels.

[10] On 11 March 1861, the church spire was struck by lightning, damaging gas lighting pipes in the steeple and igniting a beam next to the wooden roof of the chancel.

[14] A clerk at the town library noticed smoke from the north transept window and raised the alarm, enabling firefighters to save much of the historic church, including the south transept screen from c. 1500, the Norman font and a Jacobean pulpit – but the flames melted the glass in the north window and destroyed the roof, the choir room, and the majority of a rare 1756 John Snetzler pipe organ.

[15] In 1984, to mark the church's 750th anniversary, new stained-glass windows depicting the town's history from the 11th century onward were installed in the south aisle, a gift from the people of Chesterfield.

[17] In 2000, scientists were asked to evaluate the spire's movement which, although not considered a threat to the structure, had apparently accelerated during the previous two decades.

[18] In 2020, the Church was awarded a 'lifeline grant' from the Culture Recovery Fund to help ensure its continued role as a place of worship, and as a tourist attraction for the area, during the COVID-19 pandemic in the United Kingdom.

The reason is uncertain and still debated: suggestions include lack of skilled workers because of the Black Death, which occurred as much of the church was being built; the use of insufficient cross bracing and 'green timber' – unseasoned timber;[2] and also the 17th-century addition of 33 tons[24] of lead sheeting covering the spire, resting on 14th-century bracing not designed to carry such weight.

The golden cockerel weather vane atop the spire is inscribed with the names of the past vicars of St Mary's.

During the early 1800s, Chesterfield was a base for the holding of Napoleonic soldiers on parole; they were allowed a two-mile radius to roam on condition they return to barracks at the ringing of the curfew bell.

The place in which the bells are now housed once held a builders' windlass, which survives as one of the few examples of a medieval crane in existence, and the only one from a parish church.

[27] It has also been used by local companies to advertise their wares, including Scarsdale Brewery of Chesterfield, who used the spire in their logo, from 1866 until a takeover by Whitbread in 1958.

A simpler version has the devil merely sitting spitefully atop the church weather vane, its bulk causing the twisted spire and inadvertently creating a new tourist attraction.