It has been a momentous week for Justin Welby, the 105th archbishop of Canterbury. Last Saturday, he was on the global stage as he crowned King Charles III, anointing the sovereign with holy oil and issuing a resounding “God save the King!” before 2,000 people in Westminster Abbey and 20 million Britons watching on television. On Wednesday, he leveraged his status as England’s most senior cleric and the leader of the established church to castigate the government over its “morally unacceptable” migration bill. His comments made headlines and were met with predictably furious indignation from Conservative MPs and the Daily Mail. But, as they say, from the sublime to the ridiculous. On Friday, it emerged that Welby had been fined £510 with three points slapped on his licence for driving at 25mph in a 20mph zone. The archbishop was at the wheel of his VW Golf returning to his office at Lambeth Palace at the time. The most reverend and right honourable Justin Portal Welby, by divine providence lord archbishop of Canterbury, primate of all England, was, for the purposes of the notice of intended prosecution sent to Lambeth Palace, reduced to “Arch Justin Welby” by the Metropolitan police. That the case reached Lavender Hill magistrates court at all was the result of “admin errors”, according to a spokesperson for the archbishop. For Welby, the king’s coronation was a triumphant climax to mark his 10 years at the helm of the global Anglican church, an anniversary he passed in February. The ceremony at Westminster Abbey was the epitome of the pomp, ceremony, dressing up and sombre intonation that is a key component of the archbishop’s role, and one that Welby relishes. Welby said last year – before he knew he would soon be officiating at the queen’s funeral and the king’s coronation – that he planned to stay in the role until he reaches the age of 70 in 2026. Now that those two huge ceremonial events have secured his place in history, he may well conclude that another three years of interminable wrangling with church traditionalists over sexuality and reforming internal disciplinary processes have little appeal. On the other hand, Welby may wish to increasingly use his moral authority as the country’s foremost religious leader to speak truth to power. His intervention in the House of Lords this week was not the first time he has been accused of overstepping the mark on issues of social justice. He says he is political but not partisan. “One of the things I struggle with is wanting to speak the truth, but at the same time not to be party political … I’m very careful never to speak against individual politicians,” he once told a group of sixth-formers. Welby, an oil executive before he became a priest, has openly admitted to bouts of depression, for which he takes medication, and feelings of hopelessness. Some of that may be rooted in a messy childhood with alcoholic parents, the death in a car accident of his first child, Johanna, at the age of seven months, and the discovery in 2016 that he was the biological son of an aide to Winston Churchill rather the man he had believed to be his father for 60 years. The job is relentless. As well as the highly visible formal occasions – royal weddings and funerals, Christmas Day sermons at Canterbury cathedral, New Year messages to the nation – there are gruelling foreign trips, endless meetings and a huge bureaucratic institution to run. No wonder he carves out an hour early every morning for solitary prayer.