Plot: n the final programme of the series uncovering the construction and engineering skills that went into the building of Britain, Fred Dibnah indulges his personal passion for the achievements of the builders of the 19th century. Fred's final stop on this epic journey sees him scaling the heights again, this time inside the Westminster clock tower - the one we call Big Ben - where he reveals what makes the country's best-known clock tick to time and how the huge bell was originally constructed