The First Marquis
Sir Archibald Kennedy (The 1st Marquis), was born in February 1770 into the famous Clan Kennedy whose ancestral homes include Cassilis Castle and more famously Culzean Castle in Ayrshire. He was to become the 12th Earl of Cassilis upon succeeding his father but had to make do with Lord Kennedy until then!
Then he held the office of a Representative Peer [Scotland] between 1796 and 1806 which allowed him to sit in the House of Lords in England, but not as an 'English Lord' with all its rights and privileges. He was created 1st Baron Ailsa, of Ailsa, Co. Ayr on 12 November 1806 which allowed him the automatic right to a seat in the Lords. He was invested as a Fellow of the Royal Society (F.R.S.). He was invested as a Knight; Order of the Thistle (K.T.) on 17 July 1821.
On 10 September 1831 he was created 1st Marquis of Ailsa, of the Isle of Ailsa, co. Ayr, as a gift from his friend, H.R.H. William, Duke of Clarence, on his coronation as William IV in 1831. As we know, he was living in St. Margarets House. Famously, he voted for the Reform Bill which was a massively important social change of its time, changing electoral system of England and Wales.
Local Road Names
Lord Ailsa died in 1846, presumably in St. Margarets House, but definitely in Isleworth of 'Old Age' and it is a safe assumption to make that the pub was named after him.
In the same way, Ailsa Road, Ailsa Avenue and Cassilis Road would also have been named in his honour.
The area seems to have several roads named after significant locals, which from my research would appear to include the following:
Kilmorey Road, Kilmorey Gardens and Newry Road named after the Earl of Kilmorey (see 'The underground passage');
Haliburton Road; Thomas C Haliburton lived at Gordon House at the time of the 1861 census: He was a writer and Supreme Court Judge in his homeland, Canada (1841-54). Then he moved to England in 1856 and was a Member of Parliament from 1859 until his death. Famous for creating the fictional character Sam Slick.
Other Local Roads
Honywood Road; Lady Mary Anne Honywood was the oldest surviving daughter of Lady Isabella Cooper and inherited much of the local land after her mother's death (See 'Before the pub');
Percy Road; In 1594 Queen Elizabeth I granted a lease of the manor of Syon (most of the local area) to Henry Percy, 9th Earl of Northumberland on his marriage to Dorothy Devereux. The lease was upgraded to a freehold by King James I in 1604;
Redlees Close and nearby Redlees Park are located on land that was once a gravel pit (late19th/early 20th century) and formerly part of Redlees House. Redlees House was originally called Hippisley (Hippersley) House and had grounds that extended to some 17 acres. The house was purchased by Charles Farnell by 1852 and was later renamed by William Farnell Watson. (See 'The pub history').