By Michael Holden and Elizabeth Piper LONDON (Reuters) -The public must be told if British Prime Minister Boris Johnson or his staff are fined for attending parties at Downing Street during coronavirus lockdowns, opponents said on Tuesday after police said they would not name anyone issued with a fine. British police are investigating 12 possible COVID-19 rule-breaking gatherings, many held at Johnson’s office and residence, including some attended by the prime minister himself. The inquiry, which is reviewing 500 pieces of evidence and more than 300 photographs, is expected to take weeks. A l…