Nasa was furious over Dennis Tito's space trip

The Pizza Hut chain said it paid the Russian space agency about $1m (£700,000) for the promotional stunt, including footage of Mr Usachov flashing a thumbs-up after eating the pizza, and for pasting the chain's logo on a rocket last year.

Spending a long time in space has the effect of deadening the taste buds, so extra salt and spices were added to the pizza.

And salami had to be used as pepperoni lacked the necessary shelf life, growing mouldy.

Unusual customers

Some US astronauts have requested pizza after returning from space, but apparently none have eaten a slice during a mission.

The company is no stranger to making deliveries in bizarre circumstances - in 1991 they delivered pizzas to Boris Yeltsin and his supporters, who had prevailed over an attempted coup.

When food supplies dwindled in the Russian Parliament building, Mr Yeltsin called Pizza Hut delivery.

The publicity stunt however, may antagonise Russia's American counterparts on the ISS.

Nasa objected strongly when last month American space tourist Dennis Tito spent six days on the ISS, having paid a fee of $20m (£14m) to the Russian space programme.