not involved in any armed conflict with another major power. The two main political parties during the era remained the Whigs/Liberals and the Conservatives; by its end, the Labour Party had formed as a distinct political entity. These parties were led by such prominent statesmen as Lord Melbourne, Sir Robert Peel, Lord Derby, Lord Palmerston, Benjamin Disraeli, William Gladstone, and Lord Salisbury. The unsolved problems relating to Irish Home Rule played a great part in politics in the later Victorian era, particularly in view of Gladstone's determination to achieve a political settlement in Ireland. Terminology and periodisation In the strictest sense, the Victorian era covers the duration of Victoria's reign as Queen of the United Kingdom of Great Britain and Ireland, from her accession on 20 June 1837—after the death of her uncle, William IV—until her death on 22 January 1901, after which she was succeeded by her eldest son, Edward VII. Her reign lasted for 63 years and seven months, a longer period than any of her predecessors. The term 'Victorian' was in contemporaneous usage to describe the era. The era has also been understood in a more extensive sense as a period that possessed sensibilities and characteristics distinct from the periods adjacent to it, in which case it is sometimes dated to begin before Victoria's accession—typically from the passage of or agitation for (during the 1830s) the Reform Act 1832, which introduced a wide-ranging change to the electoral system of England and Wales. Definitions that purport a distinct sensibility or politics to the era have also created scepticism about the worth of the label "Victorian", though there have also been defences of it. Michael Sadleir was insistent that "in truth, the Victorian period is three periods, and not one". He distinguished early Victorianism – the socially and politically unsettled period from 1837 to 1850 – and late Victorianism (from 1880 onwards), with its new waves of aestheticism and imperialism, from the Victorian heyday: mid-Victorianism, 1851 to 1879. He saw the latter period as characterized by a distinctive mixture of prosperity, domestic prudery, and complacency – what G. M. Trevelyan similarly called the "mid-Victorian decades of quiet politics and roaring prosperity". Political and diplomatic history Early In 1832, after much political agitation, the Reform Act was passed on the third attempt. The Act abolished many borough seats and created others in their place, as well as expanding the franchise