the end of their terms. James Callaghan became Father only 4 years and 36 days after the end of his term in office, while at the other extreme Edward Heath became Father 18 years after the end of his. Number of living former PMs None Four prime ministers have been in office at a time when no former prime ministers were alive. Robert Walpole — As the first prime minister, for his entire term, April 1721 to February 1742. Henry Pelham — From the death of Robert Walpole in March 1745, until his own death in March 1754. The Duke of Newcastle — For his entire first term, June 1754 to May 1756. William Ewart Gladstone — From the death of Benjamin Disraeli in April 1881 until the end of his second term in June 1885. One Twelve prime ministers have been in office at times when only one former prime minister has been alive at or for each time. Lord Wilmington — From his appointment in February 1742 until his death in July 1743, only Robert Walpole was alive. Henry Pelham — From his appointment in August 1743 until the death of Robert Walpole, in March 1745, only Walpole was alive. The Duke of Newcastle — In his second term, July 1757 to May 1762, only the Duke of Devonshire was alive. The Duke of Devonshire — In his term, November 1756 to June 1757, only the Duke of Newcastle was alive. Lord Russell — In his second term, October 1865 to June 1866, only Lord Derby was alive. Lord Derby — In his third term, June 1866 to February 1868, only Lord Russell was alive. Benjamin Disraeli — From the death of Lord Russell in May 1878 until the end of his second term in April 1880, only Gladstone was alive. William Ewart Gladstone — From his second appointment in April 1880 until the death of Benjamin Disraeli, in April 1881, only Disraeli was alive. In his third term, February 1886 to July 1886, and in his fourth term, August 1892 to March 1894, only Lord Salisbury was alive. Lord Salisbury — In his first term, June 1885 to January 1886, and in his second term, July 1886 to August 1892, only Gladstone was alive. In his third term, from the death of Gladstone until the end of the term, May 1898 to July 1902, only Lord Rosebery