Original: It has boundaries with Warwickshire , Leicestershire , Rutland , Cambridgeshire ( including the city of Peterborough ) , Bedfordshire , Buckinghamshire ( including the borough of Milton Keynes ) , Oxfordshire , and Lincolnshire ( England 's shortest county boundary at ) .
Simplified: It has borders with Warwickshire , Leicestershire , Rutland , Cambridgeshire , Peterborough , Bedfordshire , Buckinghamshire ( including the Borough of Milton Keynes ) , Oxfordshire , and Lincolnshire ( England 's shortest county boundary : 19 metres ) .