Bertram has been a live TV announcer for over twenty five years, starting her career in 1982 with London Weekend Television. She is the longest serving female television continuity announcer in British television, and is particularly well known for her work with LWT, where she worked on and off for over twenty years - starting as a local cover announcer for Channel 4 transmission before becoming a duty announcer alongside colleagues such as Peter Lewis, Sue Peacock, Ruth Anders and Keith Harrison. Bertram and the rest of the announcing team also read short LWT News Headlines bulletins in-vision during shifts.
She left LWT in 1987 and joined the pan-European satellite channel Super Channel as an announcer and presenter before returning to London Weekend as a freelancer in 1989. Bertram next joined British Satellite Broadcasting in March 1990 and became the chief announcer for Galaxy, the company's general entertainment channel, which closed after just over eight months on-air. After a short stint contracted to TVS (where Bertram was a regular freelance announcer), she re-joined LWT again and in 1997, became the station's Senior Announcer and a relief Broadcast Manager. She was also the duty announcer for the entire ITV network on 31 August 1997 when she was called on to link the day's transmission following the death of Diana, Princess of Wales - in its capacity as nominated contractor, LWT was required to become 'ITV' for the day and transmitted to the rest of the network with Bertram as its announcer.
Alongside colleague Glen Thompsett, she made the last announcement (a recorded in-vision link) on LWT's last night as an on-air brand on 27 October 2002. Prior to LWT's on-air demise, Bertram had signed off as chief announcer on 6 October 2002. The following month, both Bertram and Thompsett began freelancing for ITV1. She joined Five shortly afterwards but continued to freelance for ITV1 as an announcer and promotions voice-over and was the only announcer to regularly be heard on air on two different terrestrial networks at the same time.
Bertram has also worked as a live announcer for Westcountry, The Family Channel and BBC World. She was also the first presentation editor for UK Gold. During the 1990s, she was the station voice for Talk Radio and for London's LBC. She went on to make guest appearances as a newspaper reviewer for the station.
Bertram continues to voice promos and pre-recorded continuity for ITV3 and Film24. She is also a regular promotions voice for QVC and provides voice overs for various companies in the corporate sector, including Microsoft (she was chosen as the voice-over for Bill Gates' presentation to the UN in 2006) as well as for BBC Local Radio, where Bertram is currently the station voice of BBC Radio Manchester and BBC Radio Leeds. She is also the station voice for Radio Pembrokeshire, Radio Scilly, Radio Caroline and The Breeze. In 2010, she also became the out-of-vision presenter for the movie magazine programme Films and Stars on Film 24.
Some of her biggest voice-over roles have been as a live stadium announcer - including the opening & closing ceremonies of the 2006 Asian Games in Doha, Qatar, the closing ceremony of the 2012 Summer Olympic Games and the opening and closing ceremonies of the 2012 Summer Paralympics in London.
Bertram has also devised various television presentation-related courses for announcers, voice-over artists, promotion producers and continuity scriptwriters. In September 2010, she was hired as the voice coach & studio director for Rosetta Stone's Advanced British English Course.