In Washington for a rapidly organised visit to introduce herself and broach one of the most sensitive issues between the United States and Britain, Ms Mowlam went down a treat. She had set the tone before departing by taking off her wig during a meeting with American reporters based in London, in a theatrical exasperation at the awful day she'd had.
She told the eight journalists sitting around a table in her office last night: "I'm going to take my hair off. I don't care about you lot. I've had enough of it today. I'm in a mood.
"I've had a bad start to the day," she went on, placing the wig on the table beside her.
Ms Mowlam is recovering from treatment for a benign brain tumour which was discovered in January, and she is delighted to be losing the weight she gained from taking steroids.
"I'm feeling in good nick and when I get my hair back, I'll be there," she said.
She also shocked leading loyalist politicians by removing her wig during a meeting in Belfast.
Once in Washington, she dined with some diehard foes of Britain's Irish policy, lunched with President Bill Clinton's National Security Adviser, and she told that noted friend of Northern Irish Catholics, Senator Edward Kennedy, why he was wrong - to his face.
What is more - by all accounts - he loved it. "He's a kindred soul," said a source close to the senator, "he's always been after energy from the British government, he'd take all her points."
What she told him was why she thought his view, that all marches in Northern Ireland should be banned, was totally wrongheaded. "Because it would benefit only one side," she later told reporters, "and there would be protests against the ban."
The official account of the Kennedy-Mowlam meeting was only a little more restrained; "It was excellent," said his office. "She's obviously committed to moving the peace process forward ... they agreed on the need to restore the ceasefire."
For another seasoned Washington commentator, Ms Mowlam was "the missing ingredient". "She's the direct antithesis of the standard, starchy British diplomat. She's great, she'll be a sensation in the job."
There were those prepared to concede, on further reflection, that what Ms Mowlam actually had to offer either side in Northern Ireland was not a great deal different from what John Major's government had offered. Ms Mowlam herself stressed that the Government - an occasional slip of the tongue also had her referring to the last government as "the Government" - required an unequivocal commitment from the IRA to a ceasefire if Sinn Fein were to participate in peace talks.
But it was the spirit in which she was embarking on her apparently thankless task that went down so well in Washington. "It's just stunning," said one convert. "The directness, the candour, the energy, they're so refreshing. What people have been looking for here is a willingness to dive in up to your eyeballs. She's it."