Will the debate over immigration affect London’s position?

London Mayor Boris Johnson was in Singapore touting for business for a couple of days.

But, instead of the usual questions over how many deals are being done, Prime Minister David Cameron's speech on curbing immigration dominated his visit.

It's unsurprising as it's an issue that I've heard repeatedly from global businesses, which is whether the pledges to control immigration will affect their ability to move workers into Britain.

Plus, as Mr Cameron vows to raise this issue with the European Union as an "absolute requirement" in the re-negotiations, it serves as a reminder of the debate over the UK's place in the EU.

That's another uncertainty that some businesses have said that they would rather not have hanging over Britain's future as they consider their long-term investment strategies.

Mr Johnson told me that it would be "nuts" to turn against immigration and emphasised that the curbs were to control benefit seekers.

Under Mr Cameron's plan, some EU migrants wouldn't be eligible for in-work, housing, and other benefits until they have worked for 4 years in the UK, for instance.

Mr Johnson emphasised the positive benefits from immigration, especially in London where 40% of the population is born outside of the UK.

When I asked him what he would do if he had his way, he said that he would aim for equality of treatment between EU and Commonwealth migrants.

In his usual colourful language, he said that Australian and New Zealand potential migrants are pretty much told to "bugger off."

He was confident that Mr Cameron's proposals wouldn't impose a negative impact on the British economy.

He says that highly skilled workers wouldn't be deterred by these potential curbs.

Still, those Singaporean and British businesses that I spoke to seemed less concerned about whether that was accurate and more concerned about the added uncertainty from another issue that could change Britain's trajectory in Europe.

Though, when it comes to the immigration debate, the business perspective is just one among many. And it seems that this will be a debate that will be with us for some time to come.