From the tenth century laws of Hywel Dda – through Chartism, the Rebecca Riots and the claim that the 1831 Merthyr Rising was the first time the red flag was raised in Britain – to the contemporary Welsh Government pledge to make Wales ‘the most LGBTQ+ friendly country in Europe’, there is a long history here of touting equality credentials. 

But as part of this narrative ‘perhaps the most fundamental thing ever invented by a person from Wales’ has often been overlooked. 

Robert Recorde, a doctor and mathematician from Tenby who lived during the turbulent sixteenth century, invented the globally familiar mathematical ‘equals’ sign. He explained his choice of two parallel horizontal lines by writing: ‘because no two things can be more equal’.

Welshman Robert Recorde from Tenby was responsible for inventing the mathematical equals signThe universally recognised mathematical symbol of the equals sign

Recorde is also credited with introducing the plus sign to English speakers, and in keeping with the polymathic pursuits of his era, also practised as a medical doctor; served the English crown as controller of several royal mints in the years following the 1536 Act of Union; and completed pioneering study of the Anglo-Saxon language, working from manuscripts recovered during the dissolution of the monasteries. 

However, when the results of Wales’ largest ever online poll was published in 2004, Culturenet Cymru’s list of ‘100 Welsh Heroes’ saw Robert Recorde placed at a lowly number 86, with just 57 votes.

Welshman Robert Recorde from Tenby was responsible for inventing the mathematical equals signNeither Robert Recorde nor his mathematical achievements are well known.

Despite the worldwide adoption of Recorde’s equality symbol, it is possible that the man and his achievements have slipped out of collective memory due to the demise of his personal fortune during his own lifetime, as he fell foul of the political and religious turmoil that followed the Protestant Reformation.

Like many notables of his era, Recorde’s precise date of birth is uncertain (variously estimated between 1510 and 1512), and his early years in Tenby are obscure, but we do know his parents were Thomas and Rose Recorde, and that their families came from Pembrokeshire and Montgomeryshire respectively.


His father had inherited a business established in the town by his own father, Roger Recorde – originally from Kent – and went on to serve as mayor of Tenby. Recorde’s mother was born Ros Johns, daughter of Thomas ap John ap Sion, from Machynlleth.

Recorde was clearly something of a prodigy, entering Oxford University at the age of 15. He was elected a Fellow of All Souls college just six years later, and went on to teach mathematics at both Oxford and Cambridge before moving to London to practise as a doctor.

Welshman Robert Recorde from Tenby was responsible for inventing the mathematical equals signThe Ground of Arts by Robert Recorde was one of the first printed English textbooks on arithmetic

Under the Tudor monarchs – who traced their ancestry to the Tudors of Penmynydd on Ynys Môn and the medieval Welsh warrior nobleman Ednyfed Fychan ap Cynwrig – talented Welshmen could attain positions that had previously been out of reach, and Recorde immediately began to climb the social ladder, working for the government from 1548.

The academic became an ally of Edward Seymour, elder brother of King Henry VIII’s third wife Jane. But like so many notable people during that period he was eventually to be deemed as belonging to the wrong side of the complex political and religious divide that characterised Wales and England in this era. 

Henry’s break from the Catholic Church in Rome was followed by the untimely death of his male heir Edward VI, the nine-day reign of Lady Jane Grey, and the ‘bloody’ incumbency of Henry’s daughter, Queen Mary I.

During the reign of the boy-king Edward VI, William Herbert, 1st Earl of Pembroke – who had himself married Anne Parr, sister of Henry VIII’s sixth wife Catherine – ran Wales and England as Lord Protector, and it was he who appointed Recorde controller of the Bristol Mint.


But when a popular revolt known as the Prayer Book Rebellion arose in Cornwall and Devon, Recorde refused to divert monies to English troops involved in its suppression without the express instruction of the king, and in so doing made the Earl of Pembroke an enemy for life. 

Herbert accused Recorde of treason, and the Welshman was confined at court for sixty days while the Bristol Mint shut down. Although Recorde was to survive this incident, bad blood with the Earl of Pembroke was eventually to lead to his demise.

Recorde’s academic work was more successful, with his first mathematical textbook The Grounde of Artes – written in the form of a dialogue between master and scholar – remaining in print for more than a century and a half, in forty editions.

In The Pathway to Knowledge (1551) he introduced the word algebra to English-speakers. Although the discipline had been used by mathematicians since its invention in the Arab world in the 9th century, the word itself did not appear until Recorde used it.

Welshman Robert Recorde from Tenby was responsible for inventing the mathematical equals signThe title page of Robert Recorde's algebra text, The Whetstone of Witte, published at London in 1557

However, the book for which Robert Recorde will be eternally remembered is The Whetstone of Whitt, in which he makes the famous claim for two parallel horizontal lines to be regarded as a symbol for equality. A digitisation of the book can be viewed online in the archive of the National Library of Wales.

This work was written during a period of great stress for the mathematician. In 1553 King Edward VI had died and under his sister Mary I many Protestant intellectuals – among whom Recorde would have counted himself – were being burned at the stake as heretics. 

Fearing for his safety, and under great pressure because of the dearth of silver production he had been responsible for overseeing during a mining operation in County Wexford, Ireland, he unwisely wrote to the queen making claims of ‘malfeasance’ (misconduct in public office) against his old enemy the Earl of Pembroke. 

Pembroke countersued for defamation, and Recorde was ordered to pay a fine of £1,000 (£250,000 in today’s money). He was imprisoned at the King’s Bench in Southwark, London, and with investigations into the silver mining operation, suspicions about his religious beliefs, and fears that he was planning to abscond the country all swirling around him, Recorde died quickly after his health deteriorated in the difficult conditions of a Tudor prison.

Welshman Robert Recorde from Tenby was responsible for inventing the mathematical equals signThis is the memorial to Robert Recorde in St Mary's Church in Tenby, Pembrokeshire

It was a sad and bitter end for an undoubtedly brilliant man whose burial place remains unknown.

But the mathematical legacy of this extraordinary Welshman lives on every time anybody anywhere in the world writes out even the simplest of sums.

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