Duckling day dawned at the University of Cambridge last week in a tradition known about by college porters but rarely glimpsed by the public. Staff sprang into action to escort a mother duck and her babies from her nesting spot in college grounds through gates, up stairs, across roads and even over a bridge to the safety of the riverbank. It’s an annual procession, but only the duck knows which day she will emerge with her ducklings in one of the courts at Corpus Christi College – and then a message is quickly sent out to other colleges to prepare for her arrival. Lee Peters, a porter at Corpu…