Getting to the White House was the easy part -

My memories of Barack Obama's inauguration are not just of the ceremony itself, but also of the exultant imagery in e-mails that came flooding into my inbox from friends and acquaintances throughout the US. "Let the healing begin," declared one, while another spoke of an event "beyond our wildest imagining". Most jubilant of all had been one from an actor who, until he crossed the Atlantic to pursue both his future wife and a career in movies, had been my closest friend.

Bob had good cause to celebrate. In the run-up to the election, he and his young bride had dug deep for Barack. Not only had they spent their evenings on the phone lines at local campaign headquarters in New York to process telephone donations, they'd even written a personal cheque for $10,000. In addition, Bob had paid a further hefty sum to attend a Democratic Party fundraiser, a gesture he considered amply justified when he found himself sitting next to the legendary crooner Tony Bennett at dinner.

I saw Bob again last week. Now the father of twin girls, he was briefly back in London, and while in town he popped round for lunch. Over our meal I reminded him of his joyful mood a year ago. I was surprised to find his reaction less than effusive. What on earth was wrong? "Oh, I don't know," he replied, picking at a cherry tomato. "I've been pretty underwhelmed with Obama. I know it's odd, but -"

His chronicle of disillusionment came out in dribs and drabs. Bob cited the various aspirations not realised, the backsliding, and the fudging on issues formerly regarded as sacrosanct. He particularly condemned Mr Obama's unwillingness to intervene during the Israeli bombing of Gaza. "But he wasn't even president then," I countered. "Surely that all occurred during George W Bush's watch? You can't blame him for that."

"I know," Bob replied moodily, pushing an asparagus spear around his plate. "But he knew about it and still did nothing. I mean, he was already president-elect." His litany continued. Most dismaying, in Bob's opinion, was the Obamas' collective obsession with celebrity. He cited Michelle turning up on an edition of the children's TV series Sesame Street, and her husband's recent appearance on the cover of a men's health magazine, giving his tips on maintaining a thin waistline. "I mean," he spluttered, "he's supposed to be the president!'

Bob quoted Henry IV's dictum on the mystique of kingship, as penned by Shakespeare: "By being seldom seen, I could not stir. But like a comet I was wonder'd at." In Bob's view, Mr Obama's craving for popularity was rapidly undermining his potency. Our debate raged across several courses. I pointed to Mr Obama's extraordinary success in pushing through fundamental reforms in American health care. Surely, I suggested, if he manages nothing else, this alone would be enough to guarantee his reputation?

And what about his sincere efforts to build bridges with hostile powers? And his leadership in bringing aid to the stricken island of Haiti? Give the man a break! Bob was sympathetic, but adamant. The politician he had helped to elect just hadn't lived up to his promises. Yet as our meal drew to an end, I slowly realised that my friend's frustration was not actually with Mr Obama, but at the new impotence of the presidential office itself.

The world has changed since the days when America cleared its throat and the rest of the world fell silent. Whether in Mr Obama's failure to bring peace to the Middle East, in his broken promise to close the detention centre at Guantanamo Bay within 12 months of coming to power, or simply in his inability to persuade China to remain at the negotiating table at the climate summit in Copenhagen - it struck me that what so frustrated my friend was not the diminishing power of the man, but of the nation he spoke for.

Being a gracious host, I did not give voice to my conclusion. But as Bob climbed into a taxi to the airport and the flight back to Manhattan and his young family, I was reminded of a quote from the writer Kent Nerburn: "It is much easier to become a father than to be one." America - and Bob - might remember that when they judge Mr Obama's first year in the White House. Michael Simkins is an actor and author based in London