One of the most prestigious prizes in mathematics has been handed out at a ceremony in Brazil.
Caucher Birkar, Alessio Figalli and Peter Scholze, and Akshay Venkatesh are all honoured for major contributions to their respective areas in mathematics.
Prof Birkar, a Kurd, came to the UK as a refugee from Iran.
The Fields Medals are awarded every four years to the most promising mathematicians under the age of 40.
Each winner receives a 15,000 Canadian-dollar cash prize.