A mutual friend, Tariq Siddiqui — a flamboyant businessman who had known Anderson since she was 16 — told her there was someone he wanted her to meet: a wonderful man he couldn’t name because it would spoil the surprise, someone who shared her passion for poetry and opera.

Anderson, a tall and attractive home counties estate agent with musical and literary inclinations, was living with her fiancé but was increasingly unhappy about the relationship. Intrigued by Siddiqui’s invitation, she accepted.

Thus, on the evening of June 9, a young woman more accustomed to the upmarket riverside pubs of Surrey and Berkshire found herself at Annabel’s, the haunt of aristocrats and their hangers on in Berkeley Square.

Siddiqui told Anderson that her date was running late. When she saw Blunkett walk in she recognised him but thought little of it. She didn’t even pay much attention when Siddiqui called out: “David, we’re over here.”

“Maybe I was being very blonde,” she told friends afterwards, “but I still didn’t get it.”

Only when Blunkett had joined them and Siddiqui winked at her did Anderson realise what was going on. Witnesses say that she looked horrified. After all, Blunkett, at 58, is twice her age. Siddiqui’s wife Lucy, taking pity, whispered: “Sally, if you want to leave, the car is outside.” But she stayed.

It was a decision with painful consquences. Last week Blunkett’s friends played down the intimacy that developed between the lonely Labour politician and the girl from the Tory heartlands. According to them she was just “someone it was pleasant to be with” — someone he had “eaten dinner with”.

That description jars alongside what her friends know of the relationship, which she told them was certainly not platonic. In recent days the publicity has led her to move out of her home and to fear for her job. But she has also received “frightening” telephone calls from people close to Blunkett and she openly talks of the inevitable “heartbreak” awaiting any woman who gets involved with him.

For the minister it has brought ridicule and renewed speculation that his political career has been terminally damaged by his lack of judgment in his personal life.

ON that first night at Annabel’s, Anderson found that she got on well with Blunkett, who had brought her a box of House of Commons chocolates. They sat in the lounge and chatted.

Because of the noise they were obliged to sit close and talk. Nobody could fail to see they made each other laugh. Blunkett can be funny when he is relaxed and it took little time for Anderson to tune in to his dry sense of humour. It seems to have helped that, like him, she hails from Yorkshire.

Nor could anybody miss Blunkett’s flirtatious side. In Anderson’s hearing he asked Siddiqui: “Does she look as good as she sounds?” And when the time came for the group to step through for dinner, Blunkett asked if she would lead him. She had never escorted a blind man, she told him nervously, but Blunkett said it would be fine so long as he stuck very close by — and slipped an arm round her waist.

As they sat down he alarmed her by going further. Only two women had ever been able to guide him satisfactorily, he said. (One was his mother.) “I’m astounded. You are the third. Excuse the pun, but it’s love at first sight.”