Following an honours degree in Law from the University of Manchester, in 1990 she joined Ulster Television where she spent three years as a news and features reporter. In 1993 she joined NBC Asia in Hong Kong as a news reporter, covering the handover of Hong Kong to China and the 1997 stock-market turmoil. She travelled extensively throughout Asia, and in Burma interviewed opposition leader Aung San Suu Kyi.
She joined ITN in April 1998 starting as Newscaster/Senior Reporter for ITV News, presenting the Early Morning News and doing special reports for News at Ten. She then became Medical Correspondent for ITV News. Having joined Five News in 2000 as a main news presenter, she moved back to ITV in 2001.
In November 2001 she was the first British journalist into Mazari Sharif after the Northern Alliance captured the city from Taliban forces. She produced a number of reports, which received wide coverage in the British press. Catherwood was reporting from inside the prison at the beginning of the Taliban prisoners uprising when one exploded a concealed grenade that killed five people. Catherwood was injured in the knee by shrapnel.
In 2003, she was promoted and made the main anchor of the ITV Weekend News, plus a relief presenter on the ITV Lunchtime News and ''ITV Evening News.
Catherwood left ITV News in September 2006, to front The Sunday Edition, ITV's new political show with Andrew Rawnsley. However, this was quietly dropped in November 2007. She has not appeared on ITV programming since.
In 2006, she was scheduled to appear on the celebrity special of The X Factor: Battle of the Stars and to sing with James Hewitt but ITV chiefs refused to give her permission to appear on the show.