In the league of ultimate predators, few flesheaters were bigger, faster and nastier than the “tyrant lizard” of popular imagination, the Tyrannosaurus rex.

Or so we thought. Now research suggests that, far from being the Ferrari of dinosaurs, the T. rex, whose ferocious reputation has fascinated generations of school children, was in fact a cumbersome creature with a maximum running speed of 15-25mph – a mere snail’s pace compared with modern animals such as the cheetah.

Unlike some of the top predators of today’s African savannah, which can change direction almost immediately, the dinosaur would have had to turn slowly or risk tumbling over. And while a human being can spin 45 degrees in a twentieth of a second, a T. rex would have taken perhaps as much as two seconds, as it would have been hampered by its long tail.

Thankfully for the T.rex, however, all its prey, such as triceratops, would have been afflicted with just the same lack of speed and agility.

The findings were reached after researchers used computer modelling and biomechanical calculations to work out the dinosaur’s speed, agility and weight. They based their calculations on measurements taken from a fossil dinosaur representative of an average T. rex and concluded that the creatures were likely to have weighed between six and eight tonnes and occasionally more than ten tonnes.

It is the first time that researchers have been able to work out the turning speed of T. rex, while the speed and weight were calculated with more certainty than in previous studies.

“We now know that a T. rex would have been front-heavy, turned slowly and could manage no more than a leisurely jog,” said John Hutchinson, of the Royal Veterinary College, University of London, who led the research.

“Previous studies have tried to find one or two numbers to estimate the mass, whereas we did over 30 computer models.”

Dr Hutchinson added: “They were not agonisingly slow and sluggish as has been suggested in the past. Nor did they have the speeds we see on the African savannah today or even the 45mph that they have been attributed with.”

Reporting their findings in the Journal of Theoretical Biology, the research team said: “ T. rex could not pirouette rapidly on one leg, as popular illustrations have sometimes pictured it and other large dinosaurs doing. All of our models should apply quite well to the large dinosaurs that T. rex likely preyed and scavenged upon.”

Calculations of the leg muscles suggest that the animal would have had a top speed of 25mph and, most likely, a usual running speed between that and 15mph. By comparison, a modern cheetah can reach 62mph, a sailfish manages 68mph and an Olympic sprinter runs at about 22mph.

It is the latest rethinking of the T. rex’s fearsome reputation. Experts have suggested that the creature was not a hunter at all, but a scavenger, although this remains a subject of debate. “We strengthen the conclusions of [previous studies] emphasising why T. rex should not have been a fast runner,” the researchers added.

An assessment of the dinosaur’s centre of gravity, slightly in from its hips, suggests that T. rex’s walking motion differed from elephants, the biggest land animal today. The dinosaur needed to bend its legs considerably, unlike elephants, which have “vertical, pillar-like” legs.

Dr Hutchison, who was based at Stanford University in the US while working on the study, suspects that the speed of the chase seen on the African savannah is the exception to predator history, rather than the rule. He believes that it is likely that the speed and agility of T. rex is more typical of the average large predator over the course of evolution.

Savannah grasslands had not developed when the dinosaurs walked the Earth and it was more likely, he said, that T. rex would have ambushed prey rather than chased them.

Monster myths

—A “spike on the nose” of the Iguanodon turned out to be a thumb claw

—The use of the Dromaeosauridae’s “second toe” was similarly disputed. It was initially considered a blade-like slashing weapon, but recent interpretations suggest that it was used for climbing

—The Pterosaur was once thought to be a cumbersome gliding dinosaur. Scientists now believe that it was probably a nimble flying reptile that may have outperformed modern birds

—The discovery in 2000 of a tiny, crow-like feathered dinosaur that could climb but not fly reopened the debate on the origin of flight

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