This W pattern appears on the outside doorways to St George's, Bradley (top - it is facing inwards on the right hand side as you enter) and the chancel doorway to St Nicolas', Great Coates (bottom - it is facing outwards on the left hand side as you look at the wall).
If I had noticed them at all during the last sixteen years, I might have assumed that they were nineteenth century graffiti by someone whose name began with W, or just possibly older 'masons marks' (forms of builder's signatures). But their similarity might have alerted me to the fact that something quite different is going on here.
It was two recorders from a Lincolnshire extension to recent East Anglican mediaeval church graffiti projects who pointed them out to me yesterday and explained that what is in fact two overlapping Vs is one of the most common devotional or superstitious marks - standing for Mary as 'the Virgin of Virgins'
At Bradley, we are almost in danger of losing the mark which is on facing stone just at the point were it is eroding away.
At Great Coates, they also pointed out a little further east (on part of the stone setting of a window) this circle which may be what is left of a 'mass dial' (a sundial intended to help the priest coming to the chancel door know when to start the Mass).
And their further discoveries inside St Nicolas' included what turn out to be two of the other most common such marks - a 'daisy wheel' pattern above and a ship below - both on the face of the pillar nearest the servery in the south-western corner of the church. The first might relate to the font which might once have been positioned there. The second might relate to the dedication of the church or be a form of intercession for a particular voyage. There is also a deeply incised cross on this pillar as well and several others elsewhere in the church.
I'm stunned by what a new pair of eyes can reveal. There is helpful background information in places like this.