In the 11th century the Duke of Aquitaine built an abbey in exchange for permission to marry a relative of his. It sounds like the ultimate form of privilege but is this fair, and what is the real story behind William’s motives?

This article explains the context behind this transaction and what the abbey looks like today.

The Duke

William was the youngest son of William the Great, and inherited the duchy in 1058.

Duke William VIII of Aquitaine, to give him his full title, is one of my maternal 24 x great-grandfathers.

He was a man of action who defeated the Saracens in 1063 in Barbastro, Spain. Historians consider this to be a proto-crusade because of Rome’s foreign policy goals.

I’ve written about the siege of Barbastro before. The main after-effects of this siege were twofold:
1 – Islamic domination over the Iberian peninsula started to fade.
2 – The Pope realised he could amass a religious army to invade another territory.

The third wife

After divorcing his second wife, William married Hildegarde of Burgundy. She was her husband’s second cousin, once removed (Cousins share grandparents, and second cousins share great-grandparents. Since his grandparents are her great-grandparents the term is “second cousin, once removed”).

It’s not clear why he chose to marry her instead of anyone else. He needed to produce a male heir because he had had only a daughter from one of his previous marriages. While exact birth dates are not available Hildegarde was about 30 years younger. Her child-bearing years would have been an attractive prospect.

The law

The predominant law at the time on the matter was Catholic canon law. The situation at the time was clear: You couldn’t marry anyone within 7 degrees of consanguinity¹. The method to calculate this was to count back to the point of a common ancestor to get the number of degrees. In William and Hildegarde’s case, this would have been 2 or 3 depending on whether you count from his or her side.

This familial situation complicated William’s life.

The promise

When William’s and Hildegarde’s first-born was a son, he had an heir. He wanted to make sure his heir would be legitimate² but what could he do?

Despite being religious and close to the Pope, William had already married Hildegarde. Perhaps it was his regal position which gave him the authority to do this, or maybe he only cared about religion when it made sense to do so. Either way, he married her in 1069, and had his first son in 1071.

To ratify his marriage and “as a form of penance” and “an act of redemption”³, William committed to build the Montierneuf Abbey^{4 5 6} in Poitiers, dedicating it to St John the Evangelist. The name comes from Old French for “montier neuf – “New monastery”⁴. It sounds like a cold-hearted transaction but the Church had form when it came to this sort of thing. In nearby Vendôme, priests had persuaded William’s parents to build another Abbey based on a random sighting of meteorites.

I wrote about the Holy Trinity Abbey of Vendôme as well.

It’s clear the church used these sort of excuses to gain property, funding for religious orders and money. We don’t know whether William proposed a church because he knew of his father’s experience, or if the church had a standing policy of making big demands.

Either way, William donated considerable amounts of land as well as money to get the job done².

Construction

Construction on the church and an abbey for 100 monks⁷ started in 1074⁸ after his heir was born. Hugh, the Grand Abbot from Cluny, oversaw the project². Cluny is far from Poitiers, making this an unusual choice, but William’s mother’s had a close connection to it. She had donated land to the Abbey in 1020. Hugh sent 18 of his monks to Poitiers². History names two of them⁷:

• Guy who became the first abbot of Montierneuf.
• The delightfully-named Ponce, described as a builder.

William died in 1086⁸, before they finished the church. He wanted to be interred in the church, and his family respected his wishes burying him in front of the main altar². (His son did the same, turning the Abbey into a necropolis of the Dukes of Aquitaine²). Pope Urbain II consecrated the church on 22 January 1096^{2 9 10}. This was more than a courtesy; it was the eve of the first crusade to the Middle East⁷. Consecrating a church built by the person who gave the papacy this idea was a key political statement.

Art and architecture

The church is characterised by the heights of its gothic apse. This is typical of constructions of the day, but from the front, its pyramidal look suggests it is much older than it is. Shouldered by flying buttresses on the east, it rests on the lower section of a late 11th-century apse. Given the many attacks and restorations, the building is now a mix of Romanesque², Gothic² and classical architecture⁷.

Unique for its time, the building uses dressed stone which explains why it has survived the test of time².

Interior

The building is a brightly-lit and airy place of worship. Rather than the gloominess of some Gothic buildings, light fills the entire church. Here it highlights the simplicity of the cut-stone masonry² and a choice few of the original 270 capitals⁷. These capitals may have had matching bases but we’ve lost these because the reconstruction raised the floor by 20 centimetres⁷.

It was not always like this. Modifications after the 17th century changed the windows to allow the volumes of natural light enjoyed today⁸. The stained glass windows are also a modern touch. The Guérithault brothers, local Poitiers glassmakers, designed the ones above the choir². The windows illustrate scenes from the life of Christ, focusing on the Passion and Resurrection. The geometric stained glass windows along the ambulatory are decorative and more recent. Makarewicz, from Limoges, installed these between 1976-1977².

The interior is straightforward – the Romanesque nave⁸ has aisles on both sides. These lead up to the transept, and a Gothic apse⁸ at the rear of the church.

Maintenance and upkeep

In 1569, Protestants besieged the town damaging the building². They also exhumed and destroyed all bodies buried in the church⁷. The original Romanesque façade was in dire condition when Abbot Pierre Rousseau de la Parisière⁷ decided to knock it down in 1640^{2 9}. The current one is set further back than the original⁷ which explains the wide open parvis. Despite Abbot Pierre’s work, the building remained in poor condition⁷.

In 1787, the state requisitioned the abbey for use as army barracks and cavalry quarters². The church became a stable for horses². This happened to many other religious buildings in France. Within less than 30 years, the Roman Catholic Church regained the building. Its new parish priest, Abbot Sabourin, saved the crumbling building by raising donations⁷. Within 5 years, the parish was operational again⁷. In 1840, the state listed the church, and 25 statues and works of art inside, as national monuments^{2 11}.

One of the few remaining decorative elements is a haut-relief of William which was on his cenotaph². This too is a national monument¹² and is in remarkable condition today.

While the minimalist style contrasts with the opulence in other French cathedrals, the nearby river makes the place humid. Any paintings that our medieval ancestors would have left would have deteriorated. I posit that this is why there aren’t more artistic flourishes, not a conscious effort to be minimalist. Apart from humidity, the church suffers from²:

• Erosion
• Crumbling
• Cracking
• Bursting of stones and of joints which are old porous or washed
• Cracked or detached restoration joints
• Other side-effects of humidity like salt development, micro-organisms and vegetation.

There are solutions to these problems. Current works on the east and south of the church will improve ventilation, rainwater recovery and water-proofing². There is also continuous restoration of the masonry, a problem that churches all over Europe suffer from.

References

1. Rootsweb.com. (2025). Canon Law and Consanguinity. [online] Available at: https://sites.rootsweb.com/~medieval/consang.htm [Accessed 17 Jan. 2025][↩]
2. L’ÉGLISE ABBATIALE SAINT-JEAN DE MONTIERNEUF. (n.d.). [online] Grand Poitiers. Poitiers, France: Direction Culture – Patrimoine. Available at: https://www.grandpoitiers.fr [Accessed 16 Jan. 2025][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩]
3. Some historical and architectural elements. (n.d.). Information board in the church, as observed by author[↩]
4. L’ÉGLISE ABBATIALE SAINT-JEAN DE MONTIERNEUF. (n.d.). [online] Grand Poitiers. Poitiers, France: Direction Culture – Patrimoine. Available at: https://www.grandpoitiers.fr [Accessed 16 Jan. 2025][↩][↩]
5. Sacred-destinations.com. (2025). St-Jean-De-Montierneuf – Poitiers, France. [online] Available at: https://www.sacred-destinations.com/france/poitiers-st-jean-de-montierneuf [Accessed 16 Jan. 2025][↩]
6. Tourisme-vienne.com. (2025). Église Saint-Jean-de-Montierneuf. [online] Available at: https://www.tourisme-vienne.com/offres/toutes-offres-patrimoine-culture/eglise-saint-jean-de-montierneuf/ [Accessed 16 Jan. 2025][↩]
7. Some historical and architectural elements. (n.d.). Information board in the church, as observed by author[↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩][↩]
8. Saint-Jean-De-Montierneuf. (n.d.). Information board near the church, as observed by author[↩][↩][↩][↩][↩]
9. Sacred-destinations.com. (2025). St-Jean-De-Montierneuf – Poitiers, France. [online] Available at: https://www.sacred-destinations.com/france/poitiers-st-jean-de-montierneuf [Accessed 16 Jan. 2025][↩][↩]
10. Tourisme-vienne.com. (2025). Église Saint-Jean-de-Montierneuf. [online] Available at: https://www.tourisme-vienne.com/offres/toutes-offres-patrimoine-culture/eglise-saint-jean-de-montierneuf/ [Accessed 16 Jan. 2025][↩]
11. Gouv.fr. (2025). Eglise Saint-Jean de Montierneuf. [online] Available at: https://pop.culture.gouv.fr/notice/merimee/PA00105595 [Accessed 16 Jan. 2025][↩]
12. Gouv.fr. (2017). Haut-relief (gisant) : Guy Geoffroy Guillaume. [online] Available at: https://pop.culture.gouv.fr/notice/palissy/PM86001536 [Accessed 16 Jan. 2025][↩]

Remember: links were correct at time of publication.