LONDON (Reuters) – Britain does not plan to pay for Russian gas in roubles, Prime Minister Boris Johnson’s spokesman said on Thursday, adding that the government was monitoring the implications for the European market of President Vladimir Putin’s demand. Putin said he had signed a decree saying foreign buyers must pay in roubles for Russian gas from April 1, and contracts would be halted if these payments were not made. Asked if there were any circumstances in which Britain would pay in roubles for Russian gas, the spokesman told reporters: “That is not something we will be looking to do.” (R…