Morgan Williams was a brewer in Putney, London in the early sixteenth century. His father, William ap Ievan, was a Welsh archer who had served with Henry VII, and like many Welshmen at the time, followed the new king to England after the Battle of Bosworth to seek his fortune. Morgan, who naturally enough, adopted the surname 'Williams' in place of the normal Welsh patronymic of 'ap William' to better fit in with his new environment, further levered himself up the social ladder by marrying Katherine, a sister of Thomas Cromwell, who just happened to be one of the most powerful men in the kingdom at the time.
Morgan and Katherine had a son, Richard, whom they placed in the service of his uncle Thomas Cromwell, and by this means he entered the court of Henry VIII. To further emphasise the link with his uncle, and no doubt further his own ambition, Richard dispensed with the 'Williams' and adopted the surname Cromwell as his own.
This newly minted Richard Cromwell won sufficient royal approval to get himself knighted and gain an estate at Hinchingbrooke in Huntingdonshire.(There were a number going spare after the Dissolution of the Monasteries. Dear uncle Thomas may have been executed in 1540, but Richard Cromwell survived and went on to serve as high-sheriff of Huntingdonshire and Cambridgeshire and take a seat in Parliament, the very model of an English squire.
His son Henry Cromwell duly inherited the estate, and his second son Robert went off and married one Elizabeth Steward, nature took its course and in the year 1599 they had a son, whom they named Oliver.
And this Oliver Cromwell, became well, that Oliver Cromwell, Lord Protector, regicide and all that.
Which is a long winded way of explaining that Oliver Cromwell's great-great-great grandfather was a Welsh brewer from Putney and that he was really a 'Williams' not a 'Cromwell'.
Scratch an Englishman....
Sourced from When was Wales? by Gwyn A. Williams (Black Raven Press, 1985) plus The Cromwell Origins at