The attacks that leveled New York City's World Trade Center will force the insurance industry to shift the way it plans for the unthinkable, the chairman of the world's biggest insurance market, Lloyd's of London, said on Wednesday. 

``We couldn't countenance this ... This is out of science fiction,'' Sax Riley said in an interview with Reuters Television in New York. ``We will have to revisit the way that we as an industry assess these realistic disaster scenarios going forward.'' 

Lloyd's, known for its complex worst-case models to assess risk, could not have imagined the scenario in which hijacked commercial aircraft slammed into the World Trade Center, collapsing the 110-story twin towers into a pile of rubble, he said. 

The devastation, which left more than 6,000 people dead or missing, was such that Riley suspected for a while that what he was seeing on television was some sort of terrible joke. 

``I thought it was a hoax,'' said Riley, who was on his way back to London when he caught a televised glimpse of the Sept. 11 attacks on the World Trade Center in the heart of New York's financial district. 

But the reality of the event sunk in, he said. 

``Then I realized that we sat on a mega mega claim,'' he said. 

Lloyd's previous worst-case scenarios were two jumbo jets colliding over a city and a hurricane ripping up the East coast of the United States, Riley said. 

Lloyd's earlier on Wednesday said it estimated that its losses from the attacks on the World Trade Center will be about $1.9 billion, (1.3 billion pounds) which would be its largest ever single payout. 

But this figure may well change in the coming months, Riley said, and insurance premiums will most likely rise after the attacks. 

The overall costs to insurers could easily exceed the record $20 billion payout from Hurricane Andrew in 1992, up to now the industry's most expensive disaster. 

The attacks are also likely to lead insurers to reassess how they insure high-rise buildings, or skyscrapers. 

Damages from the attack ripple across many sectors of Lloyd's business, Riley said. 

``This comes from all angles: aircraft, property, business interruption, workplace compensations, contingency insurance.'' 

The loss has also hit Lloyd's, which began three centuries ago in a London coffee house, very personally. 

Lloyd's has a relationship with hard-hit former World Trade Center Tenants Marsh & McLennan Cos Inc. and Aon Corp. About 200 of Aon's 1,350 employees at the World Trade Center are missing, as are 315 of Marsh's 1,900 workers. 

``This tragedy struck Lloyd's very hard ... It is a close-knit society,'' he said, adding, ``In all of history this has touched us the closest, as people.''