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The whistle blows and the beautiful game begins, but this is no ordinary football match - it is a training session for a team of robots, which on 19 July will compete at the RoboCup World Championships, hosted this year in the Chinese city of Hefei.

The knee-high footballers, based at the University of Hertfordshire, are not exactly pacey. And they are not very good at gaining possession - especially if they spot someone such as me, wearing red shoes, which they mistake for the similarly red, but round, ball because they have been programmed to spot colour rather than shape.

When they do get to the ball, they stop to look around before they kick it And once they have kicked it, they are liable to fall over.

They also kick each other, although I'm assured that will not count as a foul.

"The kicking is most likely unintentional," says their manager, Prof Daniel Polani.

"We don't yet have robots that understand that kicking will hurt other robots. He thinks that he has seen the ball."

The robots are pre-programmed - an estimated 50,000 lines of code go into preparing for a match - but there is also an element of learning.

They "speak" to their trainers as they play, explaining what they are seeing.

And when they are configured for the next match all that information can be used to raise their game.

These robots have form. In last year's competition, in Brazil, they were runners up.

But there is no room for complacency.

"We would like to win, but every game needs to be won," says Prof Polani.

"It is much harder this year, and many of the rules have changed, so we have to start again from the beginning and work our way up."

Changes include making the playing surface more like Astroturf, meaning it will be even harder for the robots to stay upright. And the ball will be white, making it harder for them to spot.

The RoboCup has been running since 1997, and each year sees ever more sophisticated robots taking part.

And it has grown from 38 teams from 11 countries to over 500 teams taking part from more than 45 countries.

It may not have as big a fan base as the World Cup, but there is no shortage of supporters cheering on the robots.

Originally conceived as a way of advancing the development of artificial intelligence, the ultimate aim is for a team of robots to take on and beat their human World Cup winning counterparts in 2050.

Watching the little guys perform, this seems unlikely - but Prof Polani remains hopeful.

"Ten years ago, this would have seemed difficult - but we have made such huge progress in the last 10 years, that it is definitely possible," he said.

"It is not entirely unrealistic."