Royal Mail might look like a first-class play on one of the world's biggest e-commerce markets. But the landmark float of the UK postal operator, expected to be worth up to £3.3 billion when it starts trading in London this month, comes with some heavy baggage.

A likely strike soon after Royal Mail's listing is a reminder of the company's Achilles' heel. The powerful Communication Workers Union should get the votes it needs to call a strike in protest over the privatisation, pensions and pay. Sure, this would be the union's first nationwide strike since 2009, and any hit to Royal Mail's sales will likely prove temporary. But the re-emergence of labour relations troubles is a concern.