From the White House to 10 Downing Street, political leaders live in some of the world's most iconic official residences. But in Canada, the fate of 24 Sussex Drive, home to the country's prime ministers for more than 70 years, is up in the air after it was allowed to fall into uninhabitable disrepair. The list of problems would turn away even the most ambitious buyer looking for a fixer-upper. The home that has welcomed the world's elite - from John F Kennedy to Princess Diana and Mikhail Gorbachev - now sits empty, a fire trap rife with asbestos, lead,...