Annoyingly, depending how you read it, the Fountain Tavern referred to might be in Hilsea and it might be in Portsmouth.
Quote
Extract of a letter from Portsmouth, Oct. 28.
“On Friday last his Grace reviewed the Duke of Richmond, accompanied by Lord Lenox, reviewed a large party of the Dragoons at Chichester, which have been quartered there sometime.
“On Saturday his Grace reviewed the Young Buffs (now in garrison at Hilsley Barracks) on Hilsey Green: They performed all the evolutions of a new exercise to admiration: His Grace went through the whole with them in person. After the review the Duke gave an entertainment to the officers at the Fountain Tavern in this garrison.
— Leeds Intelligencer, Tuesday 06 November, 1764 (source)