Complex sentence: When he researched the British RAF airfield histories, particularly those of London, Yorkshire and Lincolnshire Halpenny found that public records held very little, if any, information at all, so he had to do all the research himself going back to the very beginning.
Split into simpler sentences: When he researched the British RAF airfield histories, particularly those of London, Yorkshire and Lincolnshire. He found that public records held very little if any information at all, so he had to do all the research himself going back to the very beginning.