become more and more extreme in his views, criticising her for wearing trousers and lecturing her about the Islamic State group.

In late 2016, all the evidence indicates that Masood wanted to return yet again to Saudi Arabia - but his visa application was rejected, possibly because of his criminal record.

Frustrated, this may have the significant final event in his road to becoming a killer in March 2017.

Unbeknown at the time to their mother, Masood had a number of video calls with his young children.

In some, he talked about dreams he'd experienced - and he told the children - too young to understand what it would come to mean - that he believed he was going to die fighting for God.Bulletin of the World Health Organization

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Bringing air pollution into the climate change equation

As countries gear up for a major round of international climate talks next year in Paris, the growing problem of air pollution is fast becoming a vital part of the climate change and health debate. Fiona Fleck talks to Marit Viktoria Pettersen.

Courtesy of Marit Viktoria Pettersen

Marit Viktoria Pettersen

Marit Viktoria Pettersen is a senior advisor to the Norwegian government, and has been working on climate change and environment issues for 20 years, including as a climate negotiator for Norway. She graduated from the University of Oslo in 1994 in atmospheric chemistry. She has been involved in the work of the Intergovernmental Panel on Climate Change and received a Nobel Peace Prize certificate from the IPCC in 2007.