When PwC, the financial services firm, refurbishes its offices, foliage is a priority. “We tend to look quite closely at plants,” says Anne Muirhead, head of the firm’s future working environment. They soften the space and improve employees’ moods, as well as removing toxins and CO2 from the air, she says. “It gives a feeling of having some of the outside in the office. We do a quarterly survey and having plants around the place definitely makes people feel happier.”

The apparent triviality of the issue of office greenery can overwhelm any discussion of its benefits. In 2003, Britain’s old Department of Trade and Industry thought the matter weighty enough to draft a “Foliage Strategy” – an initiative that was duly mocked as a waste of taxpayers’ money.