Yesterday, sterling had what Bloomberg called “its biggest decline since 2010 versus the dollar”, taking it almost to a seven-year low (sterling now at $1.41 and €1.28). The fall came hot on the heels of an announcement by London Mayor Boris Johnson that he would be campaigning for the UK to leave the EU.

The prospect of sterling volatility and uncertainty between now and the referendum on 23 June 2016 will be a serious concern for corporate treasurers with cash operations in the UK.

A large number of UK companies see leaving the EU as a serious threat to jobs, investment and economic stability, so Johnson's announced support of the Leave campaign (together with support from several other prominent MPs) naturally caused nervousness throughout the financial markets, with the FTSE also suffering losses on Tuesday morning (it fell 45.51 to 5,992.22 points). Citigroup estimated on Tuesday that the likelihood of a 'Brexit' increased to 30-40 per cent, up from 20-30 per cent.

However, almost 200 UK business leaders signed a letter published today in The Times, calling for Britain to stay in the EU. They include more than a third of the UK's biggest firms. The letter states that Britain would be better off staying in a reformed European Union, as outlined by the deal negotiated by Prime Minister David Cameron. It read: “Businesses need unrestricted access to the European market of 500 million people, in order to continue to grow, invest and create jobs.”

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CTMFile take: Two-thirds of the bosses of the UK's biggest 100 business did not sign the letter. A percentage of these may be in favour of leaving the EU and some may yet be undecided. Corporate treasury could have an important role in influencing their chief executives' view on this matter.