The ex-wife of a Russian billionaire who is suing her trader son said she was shocked to learn that he had lost $50m on the stock market, in the latest twist in a titanic battle over the largest-ever divorce settlement awarded by UK courts.

Tatiana Akhmedova, who divorced her oligarch husband Farkhad Akhmedov in 2016, is now suing both him and their son Temur, 27, alleging the two men have conspired to keep most of her record £453m settlement from her. In the High Court on 8 December, Akhmedova was questioned by her son’s lawyer over the purpose of particular sums given to Temur by his father.