William Anne Capell was the first surviving son of William, 3rd Earl of Essex and his wife, Lady Elizabeth Russell, of Cassiobury Park, Hertfordshire. He was styled Viscount Malden until 1743, when he succeeded his father. He undertook his Grand Tour from 1752 to 1754, travelling from Venice with Lord Pembroke to Rome, where he was received by Cardinal Albani and had his portrait painted by Batoni (Location unknown; copy at Watford Museum). In 1754 he was recorded by Francis Macklay along with Wilson and Lords Pembroke, Thanet and Bolingbroke at Tivoli: 'The Drawing [probably for P71 Distant View of Maecenas' Villa, Tivoli] was taken on the spot by Mr Wilson in the year 1754 in Company with the Earls of Pembroke Thanet and Essex and Ld Viscount Bolingbroke who dined and spent the Day together on the Spot under a large Tree.' Although Essex is not known to have owned any paintings by Wilson his house and estate appear distantly in P134 Moor Park, Distant View towards Cassiobury.
