The major discovery was made by the architect Benjamin Ferrey in June 1870. His workmen revealed the large wall painting now seen on the south wall. Further west along the wall a badly mutilated figure of the Virgin was found, only the head-dress and crown, part of the face and upper part of the body survive, with floral border work to the east. There were also indications of coloured decoration about other parts of the church. These were not preserved.
The architect W.D.Caroe, a pupil at Ruabon Grammar School, was present at the discovery of the wall-painting which was restored by the drawing master, Mr Watt, at the expense of Chevalier Lloyd.
It appears to date from the first half of the fifteenth century. The inscription in Welsh (St Matthew 25 v 35-40) relates to the theme, the Works of Mercy, a recurrent medieval morality subject which has received various representation: sometimes as part of the ‘Tree of Life’, or as a ‘Wheel’, but here as a set of scenes. Five out of the seven biblical scenes are shown, namely: feeding the hungry, giving drink to the thirsty, clothing the naked, receiving strangers, and half of another scene with a fragment of a sixth. The treatment is fairly normal, each person performing his good deed being inspired to it by an angel: as a rule the same man is shown performing all the acts, whereas in this case the principal character is different in each scene, and in one case is a woman. The priest at Ruabon in the middle of the fifteenth century, Maredudd ap Rhys, was a skilled poet who wrote a verse to teach his parishioners the meaning of the mural. The following is a translation from the Welsh:
‘And the seven deeds (expected of) the believers,
Which should all be performed for the sake of the weak;
Supply food and drink when they come seeking,
Attend to the suffering of invalids,
Carry the dead from the hill to the church,
Befriend every jailed prisoner,
Give board and lodgings to those in need of shelter,
And clothing against the elements.’