The core of the church is Norman and is constructed from coursed and squared large sandstone blocks with ashlar dressings. The stone blocks would probably have been quarried and dressed locally.
The south aisle is the oldest part of the fabric, the walls being thicker than any other part of the building. The south porch was completed around 1600. The Gothic style is less pronounced and harmonises perfectly with the remainder of the church. Externally the chancel is more elaborate in design than the rest of the building; the cornice and parapet in particular are most unusual.
The magnificent tower was built by the Lord of the Manor, Thomas Rollestone, in 1515. Of typical Gothic design, it bears on the south side the name of the patron saint Ste Johannes. An inscription on the west face reads Ainsy et mieulx peult ester (Thus it is and better could it be) which seems to suggest that Thomas was not altogether satisfied with the finished product. A single bell was hung and is still in place as number four in a ring of six.
The bullet holes made by shots fired by Bonnie Prince Charlie's men are still visible in the West door.
The clock was installed in 1947 in memory of the Rev Dodson Tudsbury who was vicar of the parish for 28 years.
The Gothic style gabled porch built early in the seventeenth century was restored during the mid 1800s. The Norman doorway inside the porch is a fine example of Norman stone work and is in beautiful preservation with a single order of colonettes, three dimensional zigzags and pellets in the arch.
This is the oldest part of the church. The simple arched piscina (shallow basin historically used for washing communion vessels) at the east end of the south aisle indicates that the original altar was here during the early days of the church.
The octagonal stone font is dated 1514 and has a wooden cover. A law passed during the 12th century decreed that fonts should be covered to prevent the theft of holy water for use in charms and magic potions. The font was moved to its present position from the west end of the nave during the alterations in 1854.
The nave is mainly Norman and comprises three bays without a celestory (upper level). The arched bays on the south side stand on cylindrical columns and have square abaci, whereas those on the north side are clustered columns forming a quatrefoil plan and have octagonal abaci. The different patterns of the columns suggests that they were second-hand. A column at the west end of the south aisle has carved faces. The ornately carved pulpit and lectern are early 17th century. The chamfered pointed arch leading into the chancel is early 14th century. A carved dedicated inscription above the organ is dated 1893.
The three window bays are in the Decorated style of the early 14th century. The trefoil headed piscina is also early 14th century. The 17th century carved oak panelling was skilfully positioned so as to retain the piscina. The three-sided oak communion rail was made in 1660. There is believed to be only one other example of similar design country. The ornate Jacobean carving is superb with pierced panels, barley sugar' balustrades and a profusion of carved leaves and flowers.
The Holy Table was probably an Elizabethan farming house table and wear on the lower rails indicates long use for dining.
It was brought into the church in 1663 and the carving added to conform with the communion rail.
Two commandment boards flank the east window. The carved oak prayer desk was dedicated in 2005 to the memory of the late Mr Graham Charles Lawson, founder of the Mayfield and Clifton Boy Scout troop. The desk was made and presented to the church by a former Mayfield Boy Scout.
More about the architectural features are at the Corpus of Romanesque Sculpture site and the Historic England site.