We have all met monster bosses, but few people have the courage to stand up to them. Tim Field, who died aged 53 from cancer in January, devoted his life to campaigning against workplace bullies after suffering a breakdown.

He had enjoyed a successful career developing computer services until a new manager took over in 1992, and started undermining him.

After recovering from a bullying-induced breakdown, he launched the national Workplace Bullying Advice Line from his home in East Hendred, later moving to Culham Innovation Centre.

His life will be remembered in the first Tim Field memorial lecture, to be held in Oxford later this month on October 28.

It will be delivered by Professor Charlotte Rayner, of Portsmouth University, who says that bullying is not always done by the boss. Subordinates can bully middle managers, as well.

Tactics such as not delivering messages, hiding notes, changing documents, excluding people from social groups and not delivering papers for meetings in time, are all designed to make the bullied manager seem incompetent.

Prof Rayner told the British Psychological Society about one woman manager who was targeted by a group of bullies.

She said: "No matter how early she got in to work, her answerphone had been tampered with. Her actions were left off the minutes of meetings, so she appeared not to have done anything.

"She had joined a department where there were already problems. Going to work was like hell for her and she left, although she was a perfectly competent woman."

When she provided her bosses with evidence of document tampering, she was given the option of making a formal complaint, but decided her best option was to find another job, said Prof Rayner.

A survey of 1,000 employees for the Chartered Institute of People and Development found that 13 per cent had been bullied.

Of those, 12 per cent said they had been bullied by subordinates. Many experts believe this understates the problem, because both bullies and the bullied do not always recognise what is going on.

Prof Rayner said that in another survey people were asked if they had been intimidated, subjected to verbal abuse, or experienced witholding of information - all symptoms of a pattern of bullying behaviour.

They were then asked separately if they had been bullied and only half said they had been.

"Yelling or screaming at someone is relatively rare. Often it is more what people do not do. It can be very hard to say you are being bullied until the pattern emerges," she said.

Keith Munday, of the anti-bullying group Dignity at Work Now, said: "Victims of bullying who met Tim Field, read his books, consulted his website, contributed to the online discussion forum he established, or approached him for advice, knew that he was someone who genuinely appreciated from personal, first-hand experience their suffering, and was therefore able to empathise with their feelings of desperation, vulnerability and isolation.

"And, not only that, he was always someone they could rely on for help. Bearing in mind the number of messages he must have received every day, I found his capacity to respond so promptly quite awesome.

"I am sure most of us would have found his daily workload completely overwhelming.

"His achievements in the decade or so in which he so selflessly devoted his life to raising awareness of the insidious consequences of workplace abuse - at what seemed to me to be virtually every opportunity that came his way - were staggering.

"However, the sacrifices he made were undoubtedly at considerable cost to his own wellbeing.

"Tim deservedly achieved an international reputation for his pioneering work, and his ability to convey with such profound insight and clarity the true nature of bullying in the workplace.

"Tim told me that he did not expect others to do things the way he had done them; it would be up to those who followed to decide how best to set about continuing to promote the cause for which he fought so passionately.

"This is something we need to think about very carefully if we are to do justice to the memory of a good man who has left an enduring legacy for those wishing to share, and achieve, his vision of a bully-free world."

Tim Field's book, Bully in Sight (1997), became a best-seller and sold in 30 countries. In 1998, he published David Kinchin's Post Traumatic Stress Disorder: The Invisible Injury.

Then, in 2001 he co-authored and published (with Neil Marr), Bullycide: Death at Playtime, an expos of child suicide caused by bullying.

Prof Rayner's research, funded by the Department of Trade & Industry and the trade union Amicus, aims to identify effective organisational interventions into workplace bullying and harassment.

The lecture will summarise the research, focusing on the dynamics of silence and denial which lead to the acceptance of workplace bullying by UK organisations.

n Bullying Insights: Views from the Sidelines, is at the Friends Meeting House, 43 St Giles, Oxford, on October 28. For details, contact Jennie Chesterton of Oxbow (Oxfordshire Employees Bullied Out of Work) 01367 710308.

n See the website: www.bullyonline.org