Sizergh is the most northerly of the once recusant houses now owned by the National Trust, and it is, with Powis Castle in Wales, the one that had the closest links with the exiled court of James VII & II at St Germains. That link is particularly powerfully expressed by the group of pictures in the dining room, still in their original French frames, all but one of which are of James VII & II and his family. The one that is not is of his ancestor, Scotland's own royal patron saint, 'St Margaret, Queen of Scotland'. The engraving of it was dedicated to Queen Mary of Modena by the members of the Scots College in Douai, to celebrate the fact that James, Prince of Wales (the future James III), shared his birthday with the saint, whose relics they possessed.

The pictures had, indeed, originally belonged to Mary of Modena, who had given them to the former Governess of James VIII & III, 'The Old Pretender', and Bedchamber Woman to the Queen herself: Winifred Trentham, Lady Strickland (1645–1725). After the Queen's death in 1718, she retired to the English convent of Poor Clares (Franciscan nuns) at Rouen, and when she in turn died, she left all her pictures, plates and porcelain to her grandson, Thomas Peter Strickland (1701–1754).

Lady Strickland was not the only member of the family to have gone into exile with James II. Her husband, Sir Thomas Strickland (1621–1694), who was painted, probably by Jacob Huysmans, whilst married to his first wife, Jane Moseley, the widowed Lady Dawney (d.1671), was a Privy Councillor. Their eldest son, Walter Strickland (1675–1715), had been Groom of the Bedchamber to the Prince of Wales, but returned to England in 1699 to claim Sizergh, which had cleverly been put in trust by Sir Thomas, to prevent its sequestration. The third son, Roger Strickland (1680–1704), became a page to the Queen, and in 1696–1697 accompanied the Prince de Conti on his abortive expedition to Poland to be elected its King – hence the exotic costume that he wears in his portrait by Alexis-Simon Belle. Belle, who was to become court painter in France and Lorraine to James III, also painted the latter's sister, Louise-Marie; the fourth and youngest son, Thomas (c.1682–1740), later Bishop of Namur as a reward for having gone over to the Hanoverian side; and the wily Abbé Gaultier.

The Stricklands had acquired Sizergh as a consequence of the marriage of Sir William de Stirkeland of Great Strickland (it and the family name meant the pastureland of young cattle, or 'stirks') to the Deincourt heiress, Elizabeth, in 1239, but it was only his son, Sir Walter de Stirkeland (d.c.1343) who made it his principal seat, and his son, Sir Thomas (d.1376), who built the surviving tower (Westmorland and Cumberland were in those days regularly subject to raids by the Scots). In the sixteenth century the house was tripled in size, and acquired its most notable feature, The Inlaid Chamber, of c.1575–1585, whose panelling is the richest of its date anywhere in England. So exceptional is it that, having fallen on hard times, Walter C. Strickland (1825–1903), sold it for £1,000 in 1891 to the Victoria and Albert Museum, and five years later the bed and stained glass to go with it. In 1999, with great generosity, panelling, glass and bed were returned.

Walter's financial problems were, however, too grave to be solved by this sale alone, and in 1896 furniture, tapestries and pictures were put up for auction at Christie's. At that point, Walter's second cousin, Gerald, later Sir Gerald, Strickland GCMG, 6th Count della Catena (through his Maltese mother) and Baron Strickland of Sizergh (created in 1928), stepped in, acquiring much of what had been put up for auction (though Belle's superb portrait of James III escaped; it now belongs to the Government Art Collection, and usually hangs in the Scottish Office), and buying Sizergh itself, in order to relieve Walter of all his debts.

Sir Gerald, who was married to Lady Edeline Sackville, daughter of the 7th Earl De La Warr (who in 1874 lost the ownership of Knole and its contents to his brother, Mortimer, shortly thereafter created 1st Lord Sackville) was at that time Chief Secretary to the Governor of Malta. He went on to hold a succession of colonial governorships himself, before becoming a British MP and then a peer, Prime Minister of Malta between 1927 and 1932, and founder of 'The Times of Malta,' to counter the rising tide of Fascism. Despite all this, in May 1919 he was able to reopen the house, and thereafter to spend the summer months in England. His second wife, Margaret, was sister of the publishing magnate, Sir Edward Hulton. He and his first wife only had daughters, the eldest of whom, Mary, married Henry Hornyold of an old Worcestershire family, who added the name and arms of Strickland to his own in 1932. In 1950, with the consent of his son, Lieutenant-Commander Thomas Hornyold-Strickland, whose widow, née Angela Engleheart, still lives there, he donated the castle, its contents and some adjoining lands, to the National Trust.