Peter Popham: The fruits of PM's trip to Burma will be a very long time coming

He may have picked an odd day to go – the first day of the water festival, which heralds Burma's new year, when citizens joyously drench each other from dawn to dusk – but when David Cameron visits the former British colony on Friday, becoming the first British leader to do so since Anthony Eden, he will have much to talk about.

A week after Aung San Suu Kyi's crushing victory in by-elections – days after the first serious attempt to bring sanity to a business environment marked for more than 30 years by the state-sanctified lunacy of two wildly different exchange rates – Burma is suddenly Asia's new frontier.

On 23 April, the day Ms Suu Kyi takes her seat in parliament, the EU will decide whether to renew sanctions against the country that has been an international pariah since the brutal suppression of the democracy movement in September 1988. It is likely that many punitive measures will be lifted. With the National League for Democracy in parliament for the first time, and with most high-profile former political prisoners out of jail, few would dispute that Burma has turned some important corners since Ms Suu Kyi met the reforming President Thein Sein last August.

But although Mr Cameron will have a party of British businessmen in tow, experts warn against expecting quick commercial results. Derek Tonkin, a former British ambassador to Thailand and the man behind Network Myanmar, which has long advocated the lifting of sanctions, cautions that Burma will continue to promise more than it can deliver. He expects sanctions on defence sales to be retained for years to come. In many industries, he says, "local chicanery remains a hazard", with cronies of kleptocratic former generals still controlling key parts of the economy. Local partners must be able to gain entry to the economy, he said, but he pointed out that "there is no way of knowing if they are going to be in favour or go out of favour".

Mr Cameron's companions include business representatives from defence, energy and construction. Offshore gas and oil reserves, already exploited by Chevron and Total, could be rapidly expanded, Mr Tonkin says. International tourism, which has exploded in the past 18 months, offers the prospect of dependable returns for hotel-builders, and the managed float of the kyat and a planned law on foreign investment will create instant demand for financial services that have been lacking for many years. Burma is one of very few countries without ATMs, and credit cards are virtually useless.

But tourism's expansion underlines how much more needs to be done. Only a fraction of the country is open to foreign visitors, and they are likely to remain penned within tight confines as long as civil wars continue to simmer along the Thai border, in the far north and near the border with India.