The British government helped to secure a more than 240-million ($310 million) pound investment from Toyota in its English plant with a letter reassuring the Japanese carmaker over post-Brexit trading arrangements, two sources told Reuters. Toyota said on March 16 it would install its new car platform at its Burnaston plant. One source, who is familiar with the letter, said that Toyota delayed the decision due by the end of December while it weighed up a number of factors including Brexit.

The business ministry has confirmed the existence of a letter but refused to release it. The source said the letter was similar to one sent to Japanese carmaker Nissan last year when it decided to build two new models at its northern English plant. The document sparked public and lawmaker concern about secretive deals. The source, who did not say when the letter was sent, said it contained several reassurances.

"They received a similar set of warm words as Nissan on electric vehicles, commitment to further training and to ensure the competitiveness of the UK automotive industry," the source said. Britain said in March it would back up the investment from Toyota, which builds roughly 10 percent of Britain's 1.7 million cars, by spending 21.3 million pounds to support skills and training, research and development and innovation, subject to an independent assessment.