The sun comes out, the rails buckle, and speed restrictions are imposed on four lines.
Why? Because Metronet management are an incompetent bunch of cowboys. That's "incompetent" at maintaining the infrastructure, rather than incompetent at making profits, which they are remarkably good at.
In a display of timing equivalent to having your Christmas dinner in April, Metronet bosses have promised that the rails will be able to withstand heat without buckling by ... erm ... August. Great. What will happen when winter comes? Chaos as they announce that work to make the rails withstand ice will be completed by around February or so?!
What a shower. Meanwhile, it's longer journeys for drivers, more grief for station staff, and more pressure for track workers.