In written English, the first reference to the Shamrock dates from 1571, and in written Irish, as seamrog, from 1707. As a badge to be worn on the lapel on the Saint's feast day, it is referred to for the first time as late as 1681. The Shamrock was used as an emblem by the Irish Volunteers in the era of Grattan's Parliament in the 1770's, before '98 and The Act of Union. So rebellious did the wearing of the Shamrock eventually appear, that in Queen Victoria's time Irish regiments were forbidden to display it. At that time it became the custom for civilians to wear a little paper cross colored red and green.

As a symbol of Ireland it has long been integrated into the symbol of the United Kingdom, along with the Rose, the Thistle and the Leek of England, Scotland and Wales. So today, on St. Patrick's Day, a member of the British Royal Family presents Shamrock to the Irish Guards regiment of the British Army.