Interesting story.
The UK gained some 71,000 mustard gas bombs from Germany at the end of WW2 to add to its own substantial stocks so it difficult to understand why more were needed.
Perhaps the order was for research purposes though you would have thought the more modern nerve agents were more likely to be used by a potential enemy.
As an aside ICI discovered the V series of nerve agents including VX which UK goverment apparently sold in large quantities to the US!