But Mr Ellerby realised that to ensure improvements lasted, it was no good if he was the only managercommitting to training.
In early 2002, five senior managers enrolled on a development programme run by the Hay Group for four colleges in the South-east. Even this was not seen as enough.
He recalls how it had been stressed during the agency's programme for new or recently appointed principals that he was responsible for creating a climate that would allow others at the Essex college to assume greater leadership responsibilities.
"I was told it was my job to set the climate of the college," says Mr Ellerby. "If I didn't, then somebody else would, and it wouldn't be the climate that I wanted."
In 2003, some 100 middle-managers, curriculum leaders and managers of support staff attended a further programme. Mr Ellerby says that better leadership has helped to create a "common community" in the college, thus improving the quality of learning. In the meantime, Harlow's financial position has improved and is now regarded as "sound".
New staff, along with those who take on new roles, are given a mentor.
There is not normally a problem in finding people to do that job, especially among those who have had mentors . "They see it as part of their personal development," he says.
Harlow is highlighted in a study on developing aspiring leaders by the Further Education National Training Organisation (Fento). The study's findings, to be published shortly, will be used by the Centre for Excellence in Leadership to devise future programmes. The study is expected to stress the importance of strong role models in developing new leaders.
Hilary Stone, Fento's director of quality and standards, says Harlow has shown that it is not enough for principals to go on courses. "The key thing was that managers developed together as a team," she says.
David Ellerby believes Harlow operates in a climate in which everyone appreciates the vision of the college. "Leadership is about taking people forward. A good leader has to be a good communicator as well as good at understanding other people's point of view, and their roles and responsibilities," he says.