The buildings in Stanhope Place, where the Parkwood Hotel is situated, were built in the reign of William IV during the early 1800’s at the heart of a district then known as Tyburnia, located near the site of the infamous Tyburn Tree, the King's gallows between 1196 and 1783. The Tyburn tree was a huge triangular construction, the three posts were 18 feet high and the crossbeams were nine feet long - capable of hanging 24 (eight on each horizontal beam) prisoners at once. Records only show it being used at full capacity once, in 1649, but days when only one person was hanged were very rare.

Hangings were a big public festival. Most Mondays a crowd of around 10,000 people attended the executions but, when the case had received a lot of publicity, numbers could reach 50,000. The rich rented upper-storey rooms in houses and pubs along the route from Newgate Prison to the gallows (Oxford St. was part of this route and was called Tyburn Rd. at that time) so that they could get the best views. The prisoners were conveyed in open carts and the procession would stop at several inns on the way where the condemned prisoner would be offered wine. Street hawkers, thieves, pickpockets and food vendors took advantage of the holiday atmosphere and lined the route - they knew a good bet when they saw one. A grandstand was even erected at the gallows.
The hangman was entitled to the clothes of the dead, which was why some prisoners would wear their worst rags - they didn't want him to benefit too much. Some prisoners took the opposite stance and wore their finest clothes in the hope that the hangman would make it as easy as possible for them. He would then help out by pulling on their legs and beating on their chests so that they died more quickly.
The last hanging on the site was November 7, 1783, when a forger took his leave. Today, a plaque marks the approximate location of the gallows but the exact position is not known. However, the Tyburn Tree did exist very near the present site of the Marble Arch, where Bayswater Road, Oxford Street and Park Lane meet.

Interesting links

http://www.historic-uk.com/DestinationsUK/SpeakersCorner.htm
http://www.bbc.co.uk/dna/place-london/A988833
http://www.tyburnconvent.org.uk/home/index.html