Business joins the Brexit debate

For politicians supporting Britain remaining in the European Union, the blessing of business leaders is seen as a positive step.

And the list signing the pro-European letter - at least in part orchestrated by Number 10 - are certainly a hefty bunch.

But, a few health warnings.

First, many of the people who have signed have long been public advocates of Britain remaining in the EU - from Sir Roger Carr of BAE, to Iain Conn of Centrica, Dame Carolyn McCall of easyJet and Bob Dudley of BP.

Dame Carolyn McCall, Ceo of easyJet

Second, some of the business leaders named say that although Britain would be better off economically in the EU, the UK is still a significant market and investment levels would remain high whatever the outcome of the referendum.

Paul Polman, the chief executive of Unilever and one of signatories, told me that directly when I interviewed him a few weeks ago.

The UK is the world's fifth largest economy with a 60-million strong population.

As such, it matters.

Third, many smaller businesses are much more sceptical about the advantages or otherwise of the UK's membership of the EU.

A large number do not export to the rest of Europe and their only experience of Brussels is directives on employment rights which some say are over-burdensome.

The British Chambers of Commerce represents many such businesses - and it has announced it will not be campaigning for either side in the referendum as "very real divisions" exist in the business community.

US concerns

Actually, the most intriguing thing about this letter are the signatures of two banking executives few members of the general public will have heard of - Richard Gnodde and Michael Sherwood of Goldman Sachs.

Neither court the limelight but they are significant figures in the City, where the Wall Street giant employs several thousand staff and bases its European headquarters.

My banking sources agree that it is pretty unusual for their names to appear on a letter of this type.

In fact, it is the first time I believe they have done so.

It comes after Goldman Sachs pledged a large donation to the Stronger in Europe campaign.

The signal they are sending?

That the large US banks, based in London, are very concerned about Brexit and their ability to operate across the EU if it happens.

If the UK does leave, then some of their business divisions are likely to move to the continental financial centres of Frankfurt and Paris.

For those who support Brexit that might not matter much - some campaigners have dismissed them as part of the "elite establishment".

But for the City's position as a global financial centre, American banks starting to move away, even if not lock, stock and barrel, would be a significant moment.

For politicians supporting Britain remaining in the European Union, the blessing of business leaders is seen as a positive step.