'Quite obviously, you are Herr Elgar,' said Domagk in German, taking in my appearance.

Domagk was in his late thirties, tall and spare, with thinning dark hair cropped so close that the sides of his head appeared shaven. He had a neat triangle of clipped moustache and a pin through his soft white collar under the knot of his tie, American style. The little I knew of him suggested that he might begrudge spending even the small change of his time on me. He was a bacteriologist, a doctor specializing in germs, a study initiated by the Germans themselves in the 1870s. He held the title of Professor from the University of Munster-the nation which makes much of such labels has the pleasant custom of applying them without the accompanying trials of office. He had been Director of Experimental Pathology and Bacteriology at I G Farben for the past five years. I needed to dig my youthful fingers deep into my pockets of self-confidence to announce, 'Sir Frederick Hopkins asked me to pay you his respects, Herr Professor. Until last summer I was one of his students in the Biochemistry Department at Cambridge.'

'So Dr Dieffenbach explained, when he telephoned. Well, I'm sure we're honoured to welcome Sir Frederick's emissary.' I sensed no tinge of sarcasm. 'Had there been no Hopkins, our babies might still be misshapen from rickets and our sailors still dying from scurvy.'

Sir Frederick Gowland Hopkins-'Hoppy'-was President of the Royal Society, great-grandson of a captain at Trafalgar and a relation of the Jesuit priest whose poems combine subtle conciseness with eccentric metre. He was the doctor who in 1898 attended the unexpectedly early arrival of Ramsay Macdonald's firstborn in the flat downstairs at Lincoln's Inn Fields. He was also the man who discovered vitamins.

'My correspondence with Hopkins was a couple of years back, when we synthesized vitamin B1 here in these laboratories,' Domagk explained to his companion.