The castle and the associated planned town were built on the orders of King Edward III from 1361 and named in honour his wife, Queen Philippa.

Overlooking the Swale, then an important waterway approaching the River Medway, Queenborough Castle formed part of the country's coastal defences until 1650 when it was declared to be unfit for use and was almost completely demolished shortly afterwards.

The history of the castle begins in 1361, when King Edward III bought land on the Isle of Sheppey from the manor of Rushenden at the little fishing hamlet of Bynne (or Bynnee); two houses which stood on the site had to be demolished and their occupants rehoused.

It has been suggested that the new castle was more of a palace-fortress, intended as a refuge for the royal family from the Black Death which had arrived in England in the middle of the previous decade.

[9] Originally, water was channelled from the roofs through lead piping into storage cisterns, but in 1393 a contractor spent sixty weeks digging a deep well in the centre of the courtyard.

[12] In the same year, "two great guns and nine small ones" were sent from the cannon foundry at the Tower of London to Queenborough, taking priority before even Dover Castle.

[13] Upon the completion of the castle, it was visited by Edward III who created a royal charter for the town which was being laid out close by, naming it Queenborough in honour of his queen consort, Philippa of Hainault.

In 1860, the Sheerness branch line railway opened, having cut through the eastern part of the site and a pump house was built over the well, as the water was needed for the locomotives.

[18] Our knowledge of the appearance of Queenborough Castle comes from a plan in an Elizabethan manuscript preserved at Hatfield House, also from a view by Wenceslaus Hollar (1607-1677) which is now lost but is known from some 18th-century copies and impressions.

[14] The first archaeological investigation of the site was in September 1991, commissioned by Swale Borough Council prior to the enlargement of the car park towards one side.

[22] Finds included sixteen small sherds of medieval pottery, five coins and tokens, one a French jeton datable to the 15th century, and two musket balls.