In the London of 2026 St David’s Day is marked by a Wales in London Week, and all kinds of Welsh themed activities. It is quite uncontroversial.
Historically however it was the occasion of considerable prejudice against the Welsh.
Ronald Hutton’s book Stations of the Sun on folk customs and traditions notes that from the C16th with the Welsh political establishment becoming a feature in imperial London St David’s Day was symbolised by the wearing of a leek.
The response of at least some Londoners was not helpful. Hutton notes that those wearing leeks on 1st March were called ‘Taffey, or David’ and also that ‘dolls and scarecrows with leeks on their heads’ were hung from windows. it was no doubt what Nigel Farage would describe as just a bit of fun..
The Cymrophobia as it now might be called was meant with a good deal of resistance and in 1661 fights between Welshman and the London crowd are recorded.
Hutton speculates that as the centuries wore on the prejudice transferred to the Irish and Jewish populations, but its a reminder that prejudice can raise its head in many forms and always needs to be challenged where it does
Kmflett's Blog 
Interesting that at the start of Wolf Hall, Thomas Cromwell as a young boy in London understood Welsh because he had listened to the people around him in that area. Don’t know if historically accurate but Hillary Mantel did her research.