Spain and Portugal are racing the setting sun as they respond to a massive, unexplained power outage that knocked out traffic lights, caused chaos on roads and in airports, and threatened to plunge tens of millions of people into darkness on Monday.

The UK Foreign Office has issued a travel warning to UK holidaymakers after widespread power cuts hit Spain, Andorra and Portugal earlier today.

Power has mostly been restored to cities across Spain and Portugal after a major outage caused chaos yesterday. Flights, traffic lights, trains and phone networks have all been affected as the fallout continues.