Professor Alexander Thom, who died in 1985, was a distinguished engineer. Independently of his 'mainstream' academic career, he developed a deep and active interest in the prehistoric megalithic sites of Britain and Brittany. Thom's interpretations of the field data have aroused strong interest and some intense controversy.Professor Alexander Thom, who died in 1985, was a distinguished engineer. Independently of his 'mainstream' academic career, he developed a deep and active interest in the prehistoric megalithic sites of Britain and Brittany. Thom's interpretations of the field data have aroused strong interest and some intense controversy.Professor Alexander Thom, who died in 1985, was a distinguished engineer. Independently of his 'mainstream' academic career, he developed a deep and active interest in the prehistoric megalithic sites of Britain and Brittany, visiting and surveying many hundreds of them over a period of forty years. Thom's interpretations of the field data have aroused strong interest and some intense controversy. The main areas of debate are: geometry (the methods used to set out the megalithic rings, many of which appear to be non-circular); mensuration (the possible use of 'standard' units of measurement in setting out rings and rows); and astronomy (the connection between structures aligned upon the horizon and the rising and setting positions of the sun, moon or stars).Foreword; Part I. Alexander Thom's Life and Work: 1. A personal note about my late father, Alexander Thom Archie Thom; 2. A personal appreciation of Professor Alexander Thom Hans Motz; 3. The career and publications of Alexander Thom Compiled by Archie Thom; 4. A catalogue of the Alexander Thom archive held in the National Monuments Record of Scotland Lesley Ferguson; 5. The metrology and geometry of Megalithic Man Alexander Thom and Archie Thom; 6. Megalithic landscape Chris Jennings; Part II. Research Papers: Archaeological Research Inspired by Alexander Thom: 7. 'Without slÓ$