In 1947 the couple departed Australia on the Stratheden, and from September lived in Mt. Pleasant Rd., Cambridge while McTaggart worked with inorganic chemist  Harry Julius Emeléus laboratory in Downing Street. He resumed his amateur radio operation with callsign G3CUA. In 1948 he worked in Paris with Yvette Cauchois on a study concerning differences in the x-ray absorption of the elements zirconium and hafnium which they published in the Comptes Rendues' of the French Academy of Science When the need arose to separate the two metals for use in atomic reactors, their basic study contributed to further CSIRO investigations to devise an effective method.
While in Europe McTaggart visited Brussels, Eindhoven, Oslo and Porsgrunn before spending three months  from September in the US, then in January 1949 returned to Australia from Vancouver on the Aorangi, to continue work at CSIRO while living in Box Hill. Daughter Jennifer was born 8 August 1950 and in December McTaggart left CSIRO, sailing with his family on the Himalaya for employment in the UK with the British company, Laporte Industries in Luton where his work found commercial potential, and during which time he made further trips, by car, through Europe before rejoining CSIRO at the end of 1952.