The image may not be entirely fair, and colleagues point to a warm, humorous and caring personal side, but it has not done the 52-year-old workaholic any harm. It will be an enormous shock if she is not appointed general secretary of the National Association of Schoolmasters Union of Women Teachers by the end of the year.
The post is advertised to all comers this week. But Mrs Keates, already a highly respected figure in the NASUWT, has only enhanced her reputation over the past year standing in for Eamonn O'Kane, general secretary, during the illness that led to his death in May.
She is unlikely to face any serious challenge for her executive's nomination. Hank Roberts wants to stand as part of his campaign for a single merged teaching union. But he may find it difficult to secure the 25 nominations from local NASUWT associations required by mid-October.
Mrs Keates' colleagues see her as an invaluable asset who they do not intend to lose. Sue Rogers, the union's treasurer and a contemporary for 20 years, said: "The feeling in NASUWT while Eamonn was ill was, 'Thank God we have Chris. She is absolutely incredible in many respects. Her organisational ability, her retention of and attention to detail and her formidable powers of negotiation are frankly awe-inspiring."
Born and brought up in Stoke, Mrs Keates began her career as a humanities teacher in a Birmingham comprehensive in 1973. Within months she had joined the Union of Women Teachers and soon became a member of its local executive committee.
When the UWT merged with the National Association of Schoolmasters in 1976, she quickly rose through the local ranks to become Birmingham branch general secretary in 1986, and a national executive member the following year.
It was during her time at the helm in the second city in the late Eighties, a period of industrial action and unrest for teachers, that she forged her reputation as a tough, no-nonsense negotiator.
During the Nineties this often pitted her against Tim Brighouse, then Birmingham's charismatic chief education officer. She agreed with his ultimate objectives but felt that some of his experimental ideas were being introduced with "scant regard" to teacher workload.
Professor Brighouse describes his old adversary as "formidable". "People used to say in Birmingham that if you were a teacher who wanted somebody to represent you, then you couldn't get any better," he said. "She will master her brief, cover every angle and will argue fiercely on teachers' sides."
Mrs Keates was appointed NASUWT assistant secretary for policy co-ordination in 1997 and Nigel de Gruchy, then general secretary, watched her make an immediate impact on the national stage. "I could see straight away that civil servants recognised her for all the talents she had," he said. "She impressed them right from the word go."
When Mr O'Kane took over from Mr de Gruchy in 2002, Mrs Keates became his deputy. She has been labelled a "de Gruchyite" by some observers, perhaps because of her firm, pragmatic emphasis on teachers' conditions of service.
But while she admits to sharing her former leader's soundbite approach, she has also taken on board Mr O'Kane's passionate advocacy of dialogue with government. It is her desire to work constructively with whichever party is in power that prevents her from revealing her personal politics. However, her marriage to Les Lawrence, a Conservative councillor in Birmingham, made the headlines because it was seen as a union across a political divide.
She will not be pursuing Mr O'Kane's personal quest for greater professional unity. However, relations with the National Union of Teachers are likely to be smoother in future, as she gets on well with Steve Sinnott, its new general secretary. Mr Sinnott was even seen at the NASUWT's summer party, for many years a Doug McAvoy-free zone.
Mrs Keates said: "I probably come across to people as being far tougher than I actually am in taking things forward. I never wish to come across as intimidatory but I do passionately believe in what I do and believe I have a responsibility to members to do my best to act in their interests."
* August 31 Closing datefor applications.
* September 3 Shortlist of candidates drawn up.
* September 17 National executive members interview candidates and decideon preference.
* September 20 Local branch nominations open.
* October 18 They close and if no other candidate achieves at least 25 nominations the executive's candidate is announced as general secretary the following day.
* October 25 Postal ballot opens if more than one candidate is "properly" nominated.
* December 3 Ballot closes and result announced.
* January 1 New general secretary takes up post.