nerve

Prof Rubia is trying to kickstart those areas of the brain, and is working on a study looking at the trigeminal nerve – it goes directly to the brain stem and can increase activity in the frontal lobe.

After writing a few thousands words, she said, she lost her nerve.

"I lost my nerve with it and I thought I didn't have the authority to write it."

The former chief medical officer for England said she had experienced nightmares about someone picking up discarded nerve agent after the poisoning of a former spy.

In her witness statement, read to the inquiry by Francesca Whitelaw KC, Dame Sally said she had been concerned "about the disposal by the foreign agents of any residual nerve agent".