THE decision to end Royal Mail's 350-year-old monopoly on delivering letters from next January has raised the prospect of rival companies installing different coloured postboxes alongside the traditional red ones.

Customers would then choose which box to use, depending on how quickly they wanted the letter delivered and how much they had paid for a stamp.

But despite callers to radio phone-in programmes yesterday being asked if they would be prepared to ditch the UK's 115,000 Royal Mail boxes and entrust letters to a private company, the reality is likely to be different.

The decision by industry regulator Postcomm to fully liberalise the market 15 months earlier than planned is expected to affect business deliveries first.

About 80 per cent of the daily postbag of 83 million letters and packets are sent by companies, and it is this end of the market that will become the battleground.

Private companies, including Business Post, Express Dairies and Deutsche Post, of Germany, already deliver post in the UK, but their activities are limited to bulk business mail in batches of at least 4,000 letters.

Competition was first introduced in January 2003, but was restricted to 30 per cent by value of the letters market.

Full competition was planned for April 2007, the same year as the European Union was due to consider opening up the postal market across Europe.

When Postcomm proposed this in 2002, Royal Mail was known as Consignia, and was losing £1m a day as it launched a three-year renewal plan that would involve thousands of job losses and post office closures.

Since then, the organisation has returned to profit, has improved reliability and continues to dominate the £4.5bn-a-year letters business