Hamelinus Decanus (Hamelin the Dean) was a Priest in the Roman Catholic Church and founder of the Alvingham Priory.
Hamelinus established a charter which allowed 'The order of St. Gilbert of Sempringham' the creation of Alvingham Priory during the time of Pope Eugene III, between 1145 and 1153.
Hamelinus goes on to provide a gift to the Gilbertine nuns three-quarters of 'his' Parish Church of Alvingham to add to that given to them by their founder Roger, son of Jocelin.
Therefore, he must have been the Vicar of the Parish Church of Alvingham, as well as its patron and a substantial land holder.
Regardless, about he is also shown as a Prebendary of Aylesbury which at this time appeared to be a role performed by a Dean of Lincoln.