Sometime in the 16th century a small timber framed building was on this site and had probably previously been a medieval shop or market stall. 14th century deeds show a mixture of tenements, shops and market stalls.
The horse & groom was originally known as the lower rose & crown and from licensed victuallers records the first licensee was recorded in 1719 although it is more than likely that the pub was there much earlier, but records were not kept. That first licensee was peter tillier who stayed until 1721.
The cellar extends under the road on castle hill ending with an arch which was originally a passage leading to the castle, but at some point was filled in.
The first recorded licensee when the name was changed to the horse & groom was richard knight in 1792, although the property was owned by William Foster a Brewer of Windsor with a mortgage made to James Dauncey for securing £250. In 1769 the lower rose & crown was sold to Henry Reddington for £271.17 shillings and in 1837 was sold to Neville & Reid as part of the Windsor Brewery Estate.