The UK’s political spending watchdog said on Wednesday it will conduct a formal investigation into the source of funding for the refurbishment of Prime Minister Boris Johnson’s Downing Street flat. The Electoral Commission said there were “reasonable grounds” to suspect an offence had been committed. Johnson came under pressure to explain how the expensive refurbishment was paid for, after his former chief advisor Dominic Cummings said Johnson had planned to “have donors secretly pay for the renovation.” In a blog post published on April 23, Cummings said he told the prime minister that he thought the plans “were unethical, foolish, possibly illegal” and refused to help organise these payments. As a result, he said, Johnson stopped speaking to him about this matter in 2020. An Electoral Commission spokesperson said on Wednesday, “We have been in contact with the Conservative Party since late March and have conducted an assessment of the …