As members wear silk gowns of a particular design (see court dress), the award of Queen's Counsel is known informally as taking silk, and hence QCs are often colloquially called silks. Appointments are made from within the legal profession on the basis of merit rather than a particular level of experience. However, successful applicants tend to be barristers, or (in Scotland) advocates with 15 years of experience or more.
The Attorney-General, Solicitor-General, and King's Serjeants were King's Counsel in Ordinary in the Kingdom of England. The first Queen's Counsel Extraordinary was Sir Francis Bacon, who was given a patent giving him precedence at the Bar in 1597, and formally styled King's Counsel in 1603.
The new rank of King's Counsel contributed to the gradual obsolescence of the formerly more senior serjeant-at-law by superseding it. The Attorney-General and Solicitor-General had similarly succeeded the King's Serjeants as leaders of the Bar in Tudor times, though not technically senior until 1623 (except for the two senior King's Serjeants) and 1813 respectively.
But the King's Counsel emerged into eminence only in the early 1830s, prior to when they were relatively few in number. It became the standard means to recognise a barrister as a senior member of the profession, and the numbers multiplied accordingly. It became of greater professional importance to become a KC, and the serjeants gradually declined. The KCs inherited the prestige of the serjeants and their priority before the courts. The earliest English law list, published in 1775, lists 165 members of the Bar, of whom 14 were King's Counsel, a proportion of about 8.5%. As of 2010 roughly the same proportion existed, though the number of barristers had increased to about 12,250 in independent practice (i.e., excluding pupil barristers and employed barristers). In 1839 the number of Queen's Counsel was seventy. In 1882, the number of Queen's Counsel was 187. The list of Queen's Counsel in the Law List of 1897 gave the names of 238, of whom hardly one-third appeared to be in actual practice. In 1959, the number of practising Queen's Counsel was 181. In each of the five years up to 1970, the number of practising Queen's Counsel was 208, 209, 221, 236 and 262, respectively. In each of the years 1973 to 1978, the number of practising Queen's Counsel was 329, 345, 370, 372, 384 and 404, respectively. In 1989, the number of practising Queen's Counsel was 601. In each of the years 1991 to 2000, the number of practising Queen's Counsel was 736, 760, 797, 845, 891, 925, 974, 1006, 1043, and 1072, respectively.
The title traditionally depends on the sex of the sovereign. The current Queen, Elizabeth II has had a long reign, and few if any people appointed as King's Counsel survive. It can be assumed that, should the Queen die and the title pass to a descendant, the title will again become KC, as the next three in line to the throne are male heirs.