She says she hopes it is her last job change. But her departure in October after just two years at City firm DJ Freeman - where she has famously acted for George Walker and British Coal's former commercial director, Malcolm Edwards - is certain to provide her many critics with more ammunition.
The decision to set up an employment department at Clyde & Co, which is slightly older and therefore in legal terms considered more respectable than Freemans, must be seen as a sideways move. But it confirms that she is one of the few City lawyers whose profile is high enough to attract the attention of rivals. It also shows, as a friend said, that she does not 'give a toss about what people think', since she has flouted convention by swapping one partnership for another.
This is only the latest of a series of moves through the legal profession. Originally in the fashion business, she did not become a lawyer until she was 30 and had two small children. In the decade or so since, the 44- year-old Ms Kingsmill has progressed from two firms of trade union solicitors, Robin Thompson & Partners and Russell Jones & Walker, via entertainment lawyers Simkins Partnership to a five-year spell practising in her own name before joining DJ Freeman in 1990.
While her success in notable cases has won her many plaudits, she has also picked up her detractors.
Some of this can no doubt be put down to the sexism of a still male-dominated profession. But some lawyers still believe it is not playing the game to promote oneself, for example, by being pictured with clients, although the biggest firms appear to think nothing of moving into glassy monuments to corporate pride (the City's largest, Clifford Chance, is about to begin a two-month exercise moving all its staff under one huge roof in Little Britain for the first time since the merger of Clifford Turner and Coward Chance five years ago).
There have even been suggestions - rejected by founder David Freeman - that she was encouraged by DJ Freeman to seek publicity at a time when the firm was in the spotlight through making redundancies. But Ms Kingsmill is unrepentant. She feels that the marketing skills she learned in her earlier career can be of use in promoting legal services. She says: 'You can't afford to wait for clients to come in off the street.'
And while the latest move is predictable in that - rather like an unsettled footballer - she has made so many before, some will be surprised by its direction.
As a Labour Party member with a keen interest in social issues, it has been felt that the law could not hold her attention for ever and that she might be tempted into politics. However, in an interview last year, she declared being a backbench MP 'pretty boring compared with what I do now', although she was keeping her options open.
Options and opportunities crop up frequently in her conversation. Expect to hear a lot more about Clyde & Co, which Ms Kingsmill says has grown quietly but rapidly from its base as a shipping firm in recent years.
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