The Old Church in Thaon, consecrated to Saint Peter, was built from the XIth to the XIIth century in a hollow of the Mue valley, a bit apart from a former hamlet named "La Vallée". This hamlet linked with three other ones : "Thaon", "Barbières" and "Bombanville" constitued the mediaeval parish. The seigniory of Thaon was a dependency of the mighty barony of Creully which had been created by Hamon le Dentu [i.e. : Longteethed Hamon !]. In the XIIth century, the barons of Creully were in charge of the whole Bessin : from the river Orne to the river Vire. Saint Peter's church was depending of the Bayeux Cathedral and the equally on Savigny Abbey, in Manche, which owned large estates in Thaon. The power of the Creully barons and the reputation of its two protectors can easily explain the architectural quality of the Old Church.
The Old Church, as it can be seen nowadays, is composed of a chancel, a central tower and a nave that originally was fitted with two aisles : the flat apse chancel, which is slightly shifted to the South in relation to the centre line of the steeple, and the nave were built at the beginning of the XIIth century after the first sanctuary was pulled down for unknown reasons. The nave, which has five spans, originally comprised aisles the sketch of which could have been restored after excavations in 1998.
The steeple built on four strong pillars frames the oldest part of the building ; they can be dated from the years 1050 to 1070 when the upper parts were erected a few years later between 1080 and 1090. This steeple is the only remnant of a first narrower Romanesque church built at the same period, which was revealed by the first archaeological excavations.
The Old Church of Thaon has still kept up its Romanesque look with its "modillons", its chequered decoration in the south and west sides and its capitals the sculptures of which call to mind the huge sites of Bayeux and of "La Trinité" in Caen. Obviously, the church of Thaon profited by the same artists who worked in those famous neighbourings building sites.
At the XIIIth century, wide ogival bays were cut through the south wall to let more light enter the chancel. At the XVIIIth century (a bit earlier than 1729 according to the parish records), the aisles were pulled down and the wide archways of the nave were completely walled up. At the end of the XVIIIth century, in order to contend with the increasing dampness of this area the church floor and the graveyard were heightened of about thirty inches.
Between 1896 and 1900, a restoration left the capitals bare from the stonework, and the roof and the XVth century framing were reconditioned. The building, which was scheduled as a place of historic interest as far back as 1840, was soon deconsecrated when a new church was built in the new cemetery about 1845-1850. From 1994 to 1999, the Old Church was the object of a huge restoration supervised by Bruno Decaris, the head architect of the local historic monuments service : the steeple nearly falling down was wholly restored as well as the roofs of the chancel and the nave.