John Berkeley was accredited ambassador from Charles I of England to Christina of Sweden, in January 1637, to propose a joint effort by the two sovereigns for the reinstatement of the elector palatine in his dominions; probably the employment of Berkeley in this by his cousin, Sir Thomas Roe, who had conducted negotiations between Gustavus Adolphus and the king of Poland.
In 1642 he joined the Marquess of Hertford at Sherborne, and was sent into Cornwall with the rank of commissary-general to act under Sir Ralph Hopton as lieutenant-general.
The royalist forces defeated, in May 1643, the Earl of Stamford at the Battle of Stratton, with great loss of baggage and artillery, and pursued him as far as Wells.
The same year Hopton and Berkeley joined their forces to oppose Sir William Waller's westward advance, but were badly beaten at the Battle of Cheriton near Alresford in Hampshire on 29 March.
[1] After the surrender of the royalist forces, Berkeley joined his kinsman, Lord Jermyn, in attendance upon Queen Henrietta Maria.
Berkeley himself paid court to Anne Villiers, Countess of Morton, widowed in 1651; she turned him down, perhaps on advice from Sir Edward Hyde.
[1] Between 1652 and 1655 Berkeley served under Turenne in the campaigns against Condé, and the Spaniards in Flanders, accompanying the Duke of York as a volunteer.
He was considered pro-Catholic, and to favour Archbishop Peter Talbot to the extent of allowing him to use a silver plate to add to the magnificence of a religious celebration, and expressing a desire to see a high mass at Christ Church.
In December 1675 Berkeley was appointed, with Sir William Temple and Sir Leoline Jenkyns, ambassador extraordinary on the part of England at the Congress of Nijmegen then about to assemble, but bad health both delayed his departure for Nijmegen, which he finally reached in November 1676, and caused him to return the following May, before the conference finished.
In 1665, Berkeley and Sir George Carteret drafted the Concession and Agreement, a proclamation for the structure of the government for the Province of New Jersey.
Berkeley sold his share to a group of Quakers because of the political difficulties between New York Governor Richard Nicolls, Carteret, and himself.
In 1665 he began building Berkeley House, his palatial London townhouse in the Italian style, on the north side of Piccadilly, near St James's Palace in Westminster.
Berkeley was notorious for spinning incredible tales of his exploits; Clarendon wrote that through constant re-telling he may have come to believe them himself.Berkeley married Christian or Christiana Riccard, daughter of Sir Andrew Riccard, a wealthy London merchant, in the East India Company; she had already been married first to Sir John Geare, and subsequently (14 February 1659) to Henry Rich, Lord Kensington, son of Robert Rich, 5th Earl of Warwick.
He left three sons, each of whom succeeded in his turn to the title, and one daughter, Anne, who married Sir Dudley Cullum, Bart., of Hanstead, Suffolk.