Andy Burnham entered Downing Street with a swagger on Monday after his appointment to the office of prime minister by Britain’s King Charles. His first act before going in the door of number 10 was to proclaim a message of hope about his country’s future. It was such a contrast to the prosaic leadership of Keir Starmer, who lost office after two years despite a large majority in the House of Commons. Starmer’s biggest mistake was that he failed to inspire his party and the public.The contrast between the styles of the two men illustrates one of the fundamental attributes of a successful leader – the need to appear comfortable and at ease in the role. It is something Starmer never managed in his time as prime minister. The 16th-century Italian diplomat and courtier Baldassare Castiglione, whose portrait hangs in the National Gallery in Dublin, wrote that the essential attribute for a leader was “to practice in all things a certain nonchalance which conceals all artistry and makes whatever one says or does seem uncontrived or effortless”. Successful politicians have an almost mysterious ability to connect with others, make them feel at ease and convey the impression to the people they meet that they are special. Bill Clinton had this ability in spades – but all who reach the top of the greasy pole have it to some degree.Of course, charm and ease with people can only get a politician so far. If it is not accompanied by a steely determination to deliver on objectives, withstand the slings and arrows of outrageous fortune, the enmity of political opponents and the discontents of internal rivals, the charm will be exposed as artifice.The fate of Boris Johnson is a case in point. His self-deprecating humour and political ruthlessness facilitated his takeover of Downing Street in 2019. He followed that up with a hugely successful election campaign which delivered an unexpected substantial majority for his party. However, his fundamental lack of seriousness was soon exposed and his leadership collapsed in a welter of misjudgement and scandal. Burnham started off by delivering some goodies to voters, but he will soon have to take tough decisions involving increases in taxes and cuts in the bloated welfare budget if he is to have any chance of putting the UK on the path to sustainable economic growth.The UK is in a position very similar to Ireland in the 1980s, with a stagnating economy and borrowing eating up a substantial portion of tax revenue. Big changes will be required to turn the tide. Convincing his own party of the necessity for difficult decisions and following it up by getting the public on side will be the real test of his leadership. He will also need another essential ingredient of every successful political career – luck.A salutary example of how quickly things can go wrong was the fate of Brian Cowen in this country. He was widely admired in his own party before he took over the taoiseach’s office in May 2008 and the early opinion polls showed he also had wide public support.The positive mood quickly evaporated when the financial crisis struck with appalling severity a short time later. He struggled to come to terms with what was necessary to rescue the economy and didn’t convince the public about the seriousness of the challenge.In the end, Cowen and his minister for finance, Brian Lenihan, did pull the country back from the brink of financial catastrophe, but he never managed to inspire the public with the confidence he was on top of the job. The result was a political wipeout for Fianna Fáil in the 2011 general election. That catapulted Enda Kenny into the taoiseach’s office. He had endured a torrid time during his nine years as opposition leader, dealing with persistent criticism from the media, poor opinion poll results and an internal revolt that saw almost his entire front bench come out against him.Yet once he took over as taoiseach, Kenny proved to be just the leader the country needed. He and his tánaiste, Eamon Gilmore, made the necessary hard decisions. Kenny’s natural optimism was a crucial element in the success of the recovery plan and it persuaded international investors that Ireland was still open for business. [ Does salesman Andy Burnham have a product to sell?Opens in new window ]Kenny and Gilmore had to endure deep unpopularity as a result of their decisions. Gilmore ultimately lost the leadership of his party, and Kenny only managed to limp back to power as a minority government in 2016, but both men had the courage to do what was right and time has vindicated them.[ Newton Emerson: Andy Burnham likes to be liked. There could hardly be a worse qualification for the jobOpens in new window ]Whether Burnham has the stamina to go through a similar phase of unpopularity will be the ultimate test of his leadership. He is certainly better equipped than Liz Truss, who crashed and burned in a month, but he will need all his charm and a big helping of luck to restore the fortunes of his party and his country.