Who gives the government legal advice about its laws?

MPs vote to create or amend new laws in Parliament but how do they know who gives the government legal advice about the laws it wants to introduce, how they're written and then put into operation. Alma- Constance and Lucinda ask Susanna McGibbon, the government's most senior legal official in the civil service and permanent secretary of the government legal department, which provides the full range of legal services to government departments and other public bodies. Susanna tells us...