By Trevor Timpson BBC News The Last Roman's grave (ringed) was found close to the Square. Two very different finds, dug up close to each other by Trafalgar Square, shine new light on the greatest puzzle of London archaeology - the "silent" centuries after Roman rule.That the skeleton of "London's Last Roman" - or anything ancient and unknown - can be discovered in 2006 in Trafalgar Square is remarkable. But when it comes to yielding secrets, the square's church, St Martin-in-the-Fields, has a long record. When the present church was being built in the 18th Century a body was...