British spies caught between a rock and a red face

Plus, ancient Peruvians enjoyed popcorn, an American teacher is in trouble after handing out slavery-themed maths problems and more news you can lose.

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Britain has admitted for the first time that it spied on the Russians with the help of a fake rock.

The hollow rock contained electronic equipment that allowed British diplomats to receive and transmit information and was discovered in Moscow six years ago.

Russia's secret service claimed that Britain had used the rock to maintain links with human rights and pro-democracy groups.

At the time, Britain insisted that all its activities involving such groups were "completely above board". However, in a TV interview this week, Jonathan Powell, the former chief of staff for Tony Blair, the prime minister at the time, called the discovery of the rock "embarrassing", adding that the Russians "had us bang to rights".

Out for the count

An American teacher who handed out maths problems based on slavery has resigned after parents reacted with horror.

One question, given to primary school pupils in the former slave state of Georgia, posed the question: "Each tree has 56 oranges. If eight slaves pick the them equally, then how much would each slave pick?"

Another read: "If Frederick got two beatings a day, how many did he get in one week?"

The school ordered a full investigation after parents complained.

Keep your head down

In an attempt to dissuade passengers from riding on the roofs of its trains, Indonesia's state railway company is to hang concrete balls above the tracks.

The balls dangle from chains at regular intervals on frames just before and after stations. They come to within a few centimetres of the carriages, leaving "roof riders" with no option other than to jump off if they want to avoid being hit.

Several dozen people a year are killed after falling from trains. In the past, Indonesia has tried to stop the practice by spraying riders with red paint.

One rider told the Associated Press: "They've tried everything to keep us from riding. In the end we always win. We like it up there, it's windy, really nice."

Bank bonus

A teacher in West Bengal has discovered that his bank account has a balance of 490 billion rupees (US$9.8 bn).

Parijat Saha thought he had 10,000 rupees (Dh735) in his current account until he checked at an ATM. He then called the State Bank of India (SBI) to say they had made a mistake.

The bank - whose motto is "Safe Banking with SBI" - insisted that it would have been impossible for Mr Saha to use the money, which is almost equal to India's entire education budget, but officials refused to say where the billions had come from.

Pop goes Peru

Ancient Peruvians enjoyed snacking on a bowl of popcorn, new research has shown.

A study of people living on the coast of northern Peru shows they were munching popcorn at least 1,000 years earlier than previously thought.

Scientists from the Natural History Museum in Washington have been able to deduce this from corn husks dated to 4,700BC. They believe the maize was used for both flour and popcorn.