Chalmers was born in Gatley, Cheshire.^[3] Her father was an architect and her mother a medical secretary.^[4] She had a sister, Sandra Chalmers. Both sisters were educated at Withington Girls' School, an independent day school in Fallowfield near Withington, Manchester.^[5]

Chalmers began broadcasting for the BBC when she was only 13, after being selected for BBC Northern Children's Hour by producer Trevor Hill.^[6] Her younger sister Sandra, who was later editor of Woman's Hour, also performed on Children's Hour.^[7] Chalmers presented many programmes from Manchester, including Children's Television Club which later metamorphosed into Blue Peter based in London.^[8] She spent some time at secretarial college in Manchester in the early 1950s.^[9]

In the 1960s, Chalmers presented two major BBC radio programmes: Family Favourites and Woman's Hour.^[10][11] She also appeared as the original Susan in The Clitheroe Kid, and was a foil for Ken Dodd in his radio show.^[12][13] Chalmers presented ballroom dancing competition programme Come Dancing for the BBC from 1961 to 1965.^[14]

During the 1970s, Chalmers regularly presented ITV's daytime magazine programme Good Afternoon and its successors, which included Afternoon Plus and A Plus.^[15] She started presenting ITV's holiday programme Wish You Were Here? in 1974 and continued in this role until 2003, initially working alongside Chris Kelly, and later with John Carter.^[16]

In the 1980s Chalmers was a regular host of the Miss World contest on ITV, also presenting the associated UK beauty pageants such as Miss United Kingdom and the British Beauty Championships.^[17] Chalmers presented BBC Radio 2's mid-morning show from 1990 to 1992, taking over from Ken Bruce, who took over the show again following Chalmers's departure from the station in 1992.^[18]

In 2001, Chalmers appeared on Lily Savage's Blankety Blank.^[19] She took part in an episode of the BBC Two series Celebrity Antiques Road Trip, with her son Mark, in 2013.^[20]

Her television appearances in later years have been limited to short spots on chat show programmes such as Good Morning Britain, Lorraine and Graham Norton's chat shows.^[21][22][23] In 2017, Chalmers took part in Channel 5’s Celebrity Taste of Italy.^[24]

Chalmers has been married to sports commentator Neil Durden-Smith since 1964.^[25] The couple live in north London and have two children, television presenter Mark and Emma.^[26][27] Chalmers has six grandchildren.^[28]

She was awarded an OBE in 1994.^[29]