Professor Thomas Walter Bannerman Kibble passed away unexpectedly on 2 June at the age of 83. He was senior research investigator at the Blackett Laboratory and Emeritus Professor of Theoretical Physics at Imperial College, London.

He made seminal contributions to our current understanding of symmetries and symmetry breaking in the Standard Model of particle physics. He was among those who, in 1964, proposed the mechanism of spontaneous symmetry breaking in gauge theories, together with G. Guralnik and C. Hagen in the autumn of that year, following the papers by R. Brout and F. Englert and by P. Higgs.

When this new understanding was incorporated into a model proposed by S. Glashow in 1961, it lead to the first formulations of the Standard Model by S. Weinberg and A. Salam. Kibble deepened our understanding of the quantum properties of broken gauge theories for many years to come. He showed in particular how one could combine the masslessness of the photon with the short range of the weak interactions.

He was very interested in the structure of phase transitions and in symmetry breaking in the early universe. He made outstanding contributions in this field, by studying the possible existence of cosmic strings, domains, and textures, and their role in determining the large-scale structure of the universe as we see it.  

He received many honours: he was elected Fellow of the Royal Society in 1980 and won their Hughes medal in 1981, the Rutherford (1984) and Guthrie (1993) medals of the Institute of Physics, the Albert Einstein Medal (2014) and the Royal Medal of the Royal Society of Edinburgh (2014). He was awarded a CBE in the Queen’s Birthday Honours in 1998 and was knighted in 2014.

He is survived by his three children: Robert, Helen and Alison.  He was a deep thinker and a charming and humble person. He will be dearly missed.