In London, Holmes landed a job as one of its first employees at the new London-based civil and structural engineering consultancy, Ove Arup and Partners, known for its work with modern architects, its designing of unusual structures and its development of new structural techniques and materials.
When Holmes returned to the university in 1952 he was initially successful in juggling his university lecturing work with private commissions but by the mid 1950s his private work had begun to dominate and he was told by Harry Hopkins, Chair of Engineering, that it was time to choose.