The tower, with its embattled parapet, brick and flint checkerwork and diagonal buttresses at the foot, dates from the 15th century. Outside to the right of the door can be seen an empty ogee-headed (double curve, bending first one way and then the other) niche, most likely for a statue of the Virgin Mary (to whom the church is dedicated).

The door at the West End is very ancient and has to be preserved in its original condition. It has no handle or lock on it, and is secured by the time-honoured method of placing a beam across it, set into the walls. Thus it can only be opened from the inside. This offers a striking lesson to us today -in our daily lives; perhaps even as we walk around this building, Christ may be knocking at the door of our hearts. The Living Lord Jesus Christ does not force His way into our hearts and lives but like a true Lover and Friend knocks asking for admittance. He longs for us to open up our souls to His sacrificial love and eternal friendship - have we done this yet?

In the tower there are three bells and to reach the bell chamber, the visitor passes through a small door and ascends the ancient wooden and stone NEWEL (central post in a circular or winding staircase) stair carried in a projecting staircase. This stops at the first story, which was used as a Clergy Vestry in days long ago. By climbing an aluminium ladder the bell chamber is reached and although there are wooden louvered windows, little light penetrates the chamber. The 17th century bell-frame dominates the area and holds the three bell of St Mary's Church firm, consisting of wooden beams, some 6ins by 6ins, which are held by wooden pegs driven deep into each joint, the ravages of time seem to have passed the Belfry with little effect. The bells have information inscribed on them, maker date, etc. The first bell to be fitted, the Tenor has the words "Thomas Bartlett made this bell 1628" together with the founder's mark, three bells within a wreath and his name above. The second bell is 30ins in diameter with the wording "Lester & Pack of London, Fecit 1763". In good condition and appearing identical to Bartlett's bell, nothing more is known. The treble bell is the third and smallest, 28ins diameter. According to official records, i.e. "The Church Bells of Essex", by Deedes & Walters, this bell is badly broken and has the wording "RE 1694 WR" written on its waist. However the bell is no longer there and the present bell is comparatively new with the words "Recast by Gillett & Johnson, Croydon, 1933."

The ancient wooden and stone stairs are now not very safe, but it is hoped that in the not too distant future they will be repaired so all can once again climb up to look out over the whole of Chadwell and its surrounding area.

Tradition and superstition are not so strong now, but formerly there used to be a dread of the north side, where the shadow of the church fell. In the mediaeval mind, shadow was associated with the powers of darkness and evil. The mediaeval mason, in an endeavour to scare away the evil that came from the north, would carve his ugliest gargoyles on this side. High up on the embattled tower a fearsome face stills leers northward.