The Castle series or Castle High Value series are two definitive stamp series issued in the United Kingdom during Queen Elizabeth II's reign. The common aspects of the two series are the four chosen castles, one for each country of the United Kingdom.
The first series, designed by Lynton Lamb was issued in September 1955. The second, created from pictures taken by Prince Andrew, Duke of York, the Queen's second son, was issued in October 1988.
The stamps bore the highest denominations completing the Wilding and Machin definitive series. Each Castle series was replaced by Machin stamps, respectively in 1969 and 1999.