The difficulties encountered in its execution were still more formidable than those of the Worsley canal, involving carrying it across Sale Moor Moss. But the genius of John Gilbert, his agent and Brindley, his engineer, proved superior to all obstacles although at one period the duke's financial resources were almost exhausted, the work was carried to a triumphant conclusion. Both canals were completed by the time Bridgewater was thirty-six years of age, and the remainder of his life was spent in extending them and in improving his estates. During the latter years of his life he derived a princely income from the success of his enterprise. Although a supporter of Pitt's administration, he took no prominent part in politics. Wealth The duke accumulated great wealth through his canal and coal interests. His annual income was said to have exceeded £80,000. The family owned other estates: Belton House, a small Sussex estate and the Old House and, 6,000 acres (24 km2) at Ashridge. On leaving his Brackley and Worsley estates, the duke had an annual income in taxes and duties of £75,000 (estimated in 1997 as £2,360,000). The father of the first duke had bought Cleveland House in St James, London, which was rebuilt to the designs of Sir Charles Barry in 1840 and renamed Bridgewater House in 1854 for Lord Ellesmere, heir of the 3rd Duke. With the Bridgewater fortune exceeding £2,000,000, the duke, the richest nobleman in England, set about rebuilding Ashridge. He began to pull the old buildings down, but he died before his plans could be completed, leaving his heir with nothing but rubble. He was the leading member of the syndicate which purchased and partly resold the famous Orleans Collection, from the banker Jeremiah Harman in 1789. He acquired an art collection valued at £150,000 (estimated in 1997 about £4.75 million). It was composed of several old master paintings including Diana and Actaeon and Diana and Callisto. It was inherited by his heir, 1st Duke of Sutherland. Most of his purchases are still held by the Egerton family. Legacy and memorials The duke died unmarried on 8 March 1803, and the ducal title became extinct although the Earldom of Bridgewater passed to a cousin, Lieutenant-General John Egerton, who became 7th Earl). The 3rd Duke of Bridgewater was buried in the Egerton family vault in the Church of St Peter and St Paul in Little Gaddesden, close