The Unite trade union has been accused of trying to manipulate the process for choosing the Labour Party's candidate to be the Falkirk MP in the next general election. Police are now investigating allegations that the UK's largest trade union signed people up to be members of the Labour Party, without their knowledge. In the wake of the Falkirk debacle, Labour leader Ed Miliband signalled that the historic links with the unions must change.

But what happened in Falkirk? Hannah Barnes travels to the Scottish constituency to find out whether the selection process was hijacked by outside forces.

Producer: Charlotte McDonald.