On 18 June 1980, she demonstrated the multiplication of two 13-digit numbers—7,686,369,774,870 × 2,465,099,745,779—picked at random by the Computer Department of Imperial College London. She correctly answered 18,947,668,177,995,426,462,773,730 in 28 seconds. This event was recorded in the 1982 Guinness Book of Records. Writer Steven Smith said, "the result is so far superior to anything previously reported that it can only be described as unbelievable".