Harry Potter Wiki
Harry Potter Wiki

"Wenlock first scribbled down her ground-breaking theorem on the magical properties of the number seven at breakfast one day apparently on the back of an envelope, using her usual invisible ink. She then proceeded to send her cousin a letter, using what she later believed to be the very envelope concealing the theorem."
Miranda Goshawk, Book of Spells[src]

Bridget Wenlock (12021285) was a famous thirteenth-century English witch and Arithmancer, and the first to establish the magical properties of the number seven.[3] She was mainly known for being extremely protective of her theorems, therefore writing many of her ideas down in invisible ink.


Early life

Bridget Wenlock was born in the year 1202, in Tinworth, Cornwall.[1] In her youth, she attended Hogwarts School of Witchcraft and Wizardry from around 1213 to 1220, where she defied the stereotype of intelligent wizards only coming from Ravenclaw by being sorted into Hufflepuff.[5] She presumably took and studied Arithmancy class at Hogwarts from her third year onwards.


After her graduation from Hogwarts School, Bridget Wenlock studied further into Arithmancy, becoming an accomplished and celebrated Arithmancer.

Wenlock, like a number of other magical researchers, was very protective of her discoveries; her paranoia was so that she wrote exclusively in Invisible Ink, upside-down, back-to-front and in atrocious handwriting. She was also noted for her absent-mindedness, managing to promptly lose scraps of paper in which she had scribbled invisible notes. Because of this, it was not an unusual sight to see her retracing her steps through her hometown, attempting to use the Revealing Charm on every scrap of paper she came across, in search of a lost Arithmancy calculation.[1]

Bridget Wenlock in her house in Tinworth, conducting her studies in Arithmancy

It was one day, during breakfast, that Wenlock wrote the immensely famous theorem that supported the magical properties of the number seven. She wrote it down on what she thought was the back of an envelope, in the usual Invisible Ink. That same day, she posted a letter to her cousin, using what she later realised was the envelope in which she had written the theorem. Wenlock seized her broom at once, and managed to overtake the owl carrying the letter mid-flight but the owl refused to give anyone the letter but its addressee. After several nips and scratches, Wenlock had to resort to simply following the owl to her cousin's house in John O'Groats, around 600 miles away.[1]

When she finally retrieved the envelope from her cousin, a Revealing Charm revealed that it contained no more than a cake recipe. It was only when she returned to Tinworth that Wenlock found out that her calculations were scrawled on a sugar packet that was still sitting on her kitchen table.[1] It was precisely this theorem that made her such a celebrated Arithmancer for centuries to come.

At some point, Bridget presumably had children, as she had a relative by the name of Daphne Wenlock who, as of 2020, was working at an Inn at number seven, Aldwych Road in Tinworth.[4]

Death and post-mortem

Wenlock's portrait at Hogwarts Castle

Ms Wenlock died in 1285, aged around 83. In her honour, her Arithmancy achievement was recorded on a Chocolate Frog Card.[6]

There was also a portrait of her hung on the Sixth-floor corridor of Hogwarts Castle, hiding a secret passage to the Portrait Room (the password was Snafflejack).[7] There was also a bust of her on the Fat Lady's Corridor, on the seventh floor of the Castle.[8]

During his third year at Hogwarts School, sometime between 1987 and 1990, Gabriel Truman got into a big trouble for duelling a Ravenclaw Prefect, who insisted that Bridget Wenlock had come from his house. Instead of a week of detentions, Professor Sprout let him off with a warning and a box of coconut ice.[5]

Magical abilities and skills

  • Arithmancy: Wenlock was a highly accomplished and celebrated Arithmancer, who notably discovered the magical properties of the number seven. She devised many impressive numerical calculations throughout her career and was highly protective of her theorems that she had created.[3] Her knowledge and experience in this field of magic warranted her inclusion on her own Chocolate Frog Card.[6]
  • Charms: Wenlock was also talented with charm-work, as she was capable of casting the Revealing Charm, which she used to reveal the contents of many of her own personal mathematical notes and papers written in Invisible Ink.[1]

Behind the scenes

  • Interestingly, both Bridget Wenlock's first and last name are each seven letters long.
  • Her habit of scribbling her theories on paper scraps may be a reference to mathematician Pierre de Fermat who was infamous for writing his theories in the margins of his books. The most famous of these is Fermat's Last Theorem, which wasn't proven until 1994, over 300 years after his death.


The Harry Potter Wiki has 10 images related to Bridget Wenlock.

Notes and references

Professors: Septima Vector
Known Arithmancers: Sage Bragnam · Lukas Karuzos · Chiara Lobosca's father · Bridget Wenlock
Textbooks: Numerology and Grammatica · New Theory of Numerology
Arithmancy at Hogwarts: Arithmancy (class) · Classroom 7A · Advanced Arithmancy Studies
Hogwarts Castle
Locations on the seventh floor

Attic · Bean Challenge rooms · Classroom 7B · Classroom 7C · Dark Tower topmost cell · Disused bathroom · Divination Classroom · Fat Lady's Corridor · Filius Flitwick's office · Grumpy Staircase · Gryffindor Tower reading room · Gryffindor girls' staircase · Gryffindor Boys' Dormitory · Hall of Hexes · Knights' Room · North Wing · Porticus Olidus · Pungent Passage · Room of Requirement · Runic Corridor · Seventh-floor corridor · Sybill Trelawney's office · Divination corridor · Staircase to the seventh-floor corridor

Portraits, statues and other artwork located on the seventh floor

A Young Professor McGonagall · Barnabas the Barmy · Bridget Wenlock · Sir Cadogan · Caged monkey · Edward Rabnott · Elephant · Elizabeth Burke · Fat Lady · Flowering almond trees · George von Rheticus · Giraffe · Godric Gryffindor · Healers · Hippopotamus · Journeying wizards · Lachlan the Lanky · Mother and baby · Oraclitus Spheer · Staring Portrait · Three young ladies · Tiger · Two lovers in a graveyard · Valeria Myriadd · Wailing Egyptians · Witch flying to the moon · Wizard in black flowing robes · Wizard in blue · Wizard with a broomstick · Wolfhound

Albus Dumbledore-101-chocFrogCard.png
Chocolate Frog Cards
Gold cards

Armando Dippet · Albus Dumbledore · Barberus Bragge · Bertie Bott · Carlotta Pinkstone · Dzou Yen · Godric Gryffindor · Harry Potter · Herpo the Foul · Helga Hufflepuff · Montague Knightley · Phillipus von Hohenheim · Rowena Ravenclaw · Salazar Slytherin

Silver cards

Alberic Grunnion · Alberta Toothill · Andros the Invincible · Artemisia Lufkin · Blenheim Stalk · Bowman Wright · Chauncey Oldridge · Circe · Cliodna · Crispin Cronk · Cyprian Youdle · Daisy Dodderidge · Derwent Shimpling · Donaghan Tremlett · Dunbar Oglethorpe · Dymphna Furmage · Elfrida Clagg · Felix Summerbee · Fulbert the Fearful · Gaspard Shingleton · Gideon Crumb · Glenda Chittock · Gondoline Oliphant · Gregory the Smarmy · Gwenog Jones · Honoria Nutcombe · Ignatia Wildsmith · Joscelind Wadcock · Kirley Duke · Laverne de Montmorency · Leopoldina Smethwyck · Maeve · Mirabella Plunkett · Mopsus · Morgan le Fay · Oswald Beamish · Roderick Plumpton · Sacharissa Tugwood · Thaddeus Thurkell · Wendelin the Weird · Xavier Rastrick

Bronze cards

Adalbert Waffling · Almeric Sawbridge · Archibald Alderton · Balfour Blane · Beatrix Bloxam · Beaumont Marjoribanks · Bridget Wenlock · Burdock Muldoon · Cassandra Vablatsky · Celestina Warbeck · Cornelius Agrippa · Devlin Whitehorn · Dorcas Wellbeloved · Edgar Stroulger · Elladora Ketteridge · Ethelred the Ever-Ready · Flavius Belby · Gifford Ollerton · Glanmore Peakes · Glover Hipworth · Greta Catchlove · Grogan Stump · Gulliver Pokeby · Gunhilda de Gorsemoor · Havelock Sweeting · Hengist of Woodcroft · Heathcote Barbary · Herman Wintringham · Hesper Starkey · Jocunda Sykes · Justus Pilliwickle · Merlin · Merton Graves · Merwyn the Malicious · Miranda Goshawk · Mungo Bonham · Musidora Barkwith · Myron Wagtail · Newton Scamander · Norvel Twonk · Orsino Thruston · Perpetua Fancourt · Quong Po · Roland Kegg · Stoddard Withers · Tilly Toke · Uric the Oddball · Yardley Platt

Famous Vampires cards

Blodwyn Bludd · Vlad Drakul · Amarillo Lestoat · Carmilla Sanguina · Herbert Varney

Famous Hags cards

Babayaga · Malodora Grymm · Old Mother Hubbard · Cordelia Misericordia · Leticia Somnolens

Famous Giants cards

Bran the Bloodthirsty · Cyclops · Goliath · Morholt · Hengist of Upper Barnton

Famous Goblins cards

Alguff the Awful · Eargit the Ugly · Gringott · Ug the Unreliable · Urg the Unclean

Dragon cards

Common Welsh Green · Hebridean Black · Hungarian Horntail · Norwegian Ridgeback · Romanian Longhorn

Beast cards

Billywig · Bowtruckle · Doxy · Double-ended Newt · Giant Purple Toad · Giant Squid · Gnome · Gytrash · Imp · Kelpie · Manticore · Mountain Troll · Streeler · Phoenix · Unicorn