Nobel Prize laureates Peter Higgs and Francois Englert on Saturday received honorary degrees at an event in Edinburgh.
At a graduation ceremony in the University of Edinburgh's McEwan Hall, Professor Higgs of the University of Edinburgh and Professor Englert of the Free University of Brussels received doctorates in science from one another's institutions.
Higgs and Englert won the Nobel Prize for Physics in 2013 for independently discovering a mechanism that enables elementary particles to acquire mass.
The new subatomic particle predicted by the mechanism, the Brout-Englert-Higgs boson, was confirmed to exist in 2012 following ground-breaking experiments at the European Organization for Nuclear Research (CERN) near Geneva.
At the event, Professor Sir Tom Kibble from Imperial College London, who also developed the theory of the mechanism, received a Royal Medal from the Royal Society of Edinburgh.
Professor Rolf-Dieter Heuer, Director-General of CERN, was awarded an honorary degree from the University of Edinburgh.
At the ceremony, Professor Higgs was also awarded the Freedom of the City of Edinburgh by the Lord Provost Donald Wilson.
Professor Tom Insel, Director of the National Institute of Mental Health in Bethesda in west central Maryland of the United States, received an Honorary Doctor of Science from the University of Edinburgh.