By Estelle Shirbon LONDON (Reuters) – Princes William and Harry walked side by side behind their grandmother Queen Elizabeth’s coffin on Wednesday, a scene reminiscent of when, as boys 25 years ago, they followed their mother Princess Diana’s casket in the glare of global media. The brothers, whose relationship has become strained in recent years, were taking part in a solemn procession from Buckingham Palace to Westminster Hall, where the queen’s body will lie in state for four days until her funeral on Monday. Their father King Charles was just in front of them with the late queen’s other ch…