Mannie works as an organisation development and change consultant in health and social care, industry, the financial sector, public protection agencies, faith organisations, the arts, charities, voluntary organisations and professional associations.

He concentrates on redefining organisational aims, introducing new operational strategies, addressing staff morale, fostering inter-dependent systems of work and understanding the role of technology. He works on intra- and inter-group relatedness; group belief systems; group identity, role, task, authority, culture and the exercise of authority and leadership.

Mannie has a special interest in the part thought and thinking plays in strategic development and the operations of organisations and is currently undertaking research in this area. In 1997, he was appointed Director of the Group Relations Programme of the Tavistock Institute.