University of California Emeritus Professor Richard Muller says it's "frighteningly easy" to scientifically change the nature of a coronavirus in the lab to optimize its impact. The remarks come following a report published in the Wall Street Journal on the origins of COVID-19, of which Professor Muller was co-author. "It's frighteningly easy to do. The insertion of this double sig molecule it's something that had been done before by the scientists at Wuhan," he told Sky News host Chris Smith. "They had done it not for this virus but for others, they had published that, it was done about 11 or 12 times in laboratories around the world. So this gene splicing is not hard to do. "The thing that gave it away was that they used the gene splice that everybody else uses. It's very unusual to have the double sig sequence in coronavirus, in fact the double sig sequence has never been seen in this whole class of coronaviruses. "But it is the one that is most used in the laboratory. So this thing was stuck in through simple gene splicing, it doesn't leave any trace, except for the fact that it's there. "The second thing they did was the optimisation and this is gain-of-function, it likewise doesn't leave any special record other than this unusual feature that it is pre-optimised for humans."