Bishop Geoffroy d'Eu is explicit about this in the 1236 charter, and gives the merit to Evrard de Fouilloy (died 1222), Gallia Christiana X, col 342, transcribed in item 12 below: "Quoniam per clarae memoriae episcopum Everardum fuerat ordinatum... quatenus fundamenta ecclesiae ampliaret....". Further defined in the 1241 charter transcribed in item 16 below, Cartulaire, I 362-363, "...per eundem Everardum, episcopum, accedente consensu cleri et populi Ambianensis, fuerat ordinatum, et erat necesse quatinus fundamentum dicte ecclesie ampliaret....". The inscription around the tomb of Bishop Evrard transcribed in item 4 below also mentions foundations, "...qui fundamenta locavit huius structurae...". The exact date (1220) is supplied by the labyrinth, set sixty eight years later, in 1288. The labyrinth was destroyed in the 1820s and replaced between 1894 and 1897 under the direction of Lisch and Billoré. The new inscription was engraved by Frennelot under the direction of Georges Durand. In the center of the labyrinth was an octagonal stone bearing images of four personages and carrying an inscription around the edge. The inscription is recorded in a fourteenth-century martyrology and register of the distributions of the chapter of Amiens, Arch. Somme, G 2975 fol. 247 ro.

Note on when this church was begun. Just as
it is written in the slab of the House of Daedalus.
In the year of grace 1220
was this work
first begun. At that time
the bishop of this diocese was Evrard
blessed bishop. And the king of France
was Louis who was the son of Philip the wise*.
He who was master of the work
was named Master Robert and
surnamed de Luzarches. Master
Thomas de Cormont was after him
and afterwards his son Master Renaud
who had this inscription placed
at this place in the year of incarnation

*Note: Louis VIII, son of Philip Augustus, came to the throne in 1223, not 1220. The labyrinth text has been transcribed many times, see, for example, G. Durand, Monographie, I, 23, and E. Soyez, Labyrinthes, 23.

The 1220 date was also recorded in an inscription 13 metres long (clumsily restored) over the south transept portal: "EN LAN Q LINCARNATIO VALOIT MCC & XX (5 metre lacuna) ORS IFV RIMIST LE PREMIERE PIERE IASIS .... LE CORS (70 centimetre lacuna) ROBERT (90 centimetre lacuna)" G. Durand, Monographie, I, 24, lamented the impossibility of interpreting this mutilated inscription.

The Corbie Chronicle V compiled by Anthoine de Caulaincourt in the early sixteenth century placed the start of work not in 1220, but in 1223, Amiens, BIbl. mun.,MS 524, 172-173 (old pagination, 80ro-81vo) "Tempore ipsius Hugonis anno primo videlicet quo fuit Abbas, templum maius B. Mariae Ambianensis indicibili prope tam impensa tam artis elegantia construi coeptum est sub Emerardo Ambianensi Episcopo et consummatur anno 1264, quo construi coeptum fuerat, quod certe inter totius Regni Francorum templa nullum pulchrius creditur."

The start of work is placed in the first year of Hugo, who became abbot (p. 157, old pagination, 79vo) in 1223. The accuracy of the Corbie Chronicle was questioned by G. Durand, Monographie, I, 37.

The antiquarians of Amiens, presumably on the authority of the labyrinth, place the start of work in 1220, see, for example, Bibl. nat., Collection de Picardie, II, J.-J. de Court, Memoires cronologiques, II, 2, "Ce fut en 1220 que cet Eveque jetta les fondemens de ce merveilleux temple, non pas entierement, car comme l'eglise collegiale de S. Firmin Confesseur se trouvoit dans l'espace du terrain que devoit embrasser cette nouvelle eglise, il falut prendre des mesures pour la demolition de cette collegiale, ce qui ne pu se faire du tems de ce prelat qui mourut trois ans apres, n'aiant fait elever cet ediffice qu'hors de terre."