Written and first recorded by Kristy MacColl (1979).
Hit version by Tracey Ullman (UK #2 1983 |US #8/MOR #11 1984).
Also recorded by Anja Niskanen (1984), Ben Gibbard (2010).
From the wiki: “‘They Don’t Know’ was written by Kristy MacColl, who recorded it in 1979. It became popular on radio in the United Kingdom, reaching #2 on the Music Week airplay chart. However, complications involving a strike at her record distributor prevented the single from being shipped and promoted properly. MacColl’s version of ‘They Don’t Know’ thus failed to appear on the official UK Singles chart, which is entirely sales-based.
“In 1983, Tracey Ullman recorded a version of the song. Already well-known in the UK as an actress and comedienne, ‘They Don’t Know’ was issued as her second single there, reaching #2. MacColl performed backing vocals on Ullman’s version and reprised her original ‘bay-ay-be-ee’ in the middle of the song. The song was also included on Ullman’s debut album, You Broke My Heart in 17 Places.
“The track was released in the United States the following year, as Ullman’s first single there. At the time, Ullman was almost a complete unknown in the US, as her TV appearances had not been seen in that country. Publicity for the single was aided by the fact that the video for ‘They Don’t Know’ featured a cameo from Paul McCartney. (At the time it was filmed, Ullman was filming a minor role in McCartney’s film Give My Regards To Broad Street.) ‘They Don’t Know’ eventually reached #8 on the Billboard Hot 100.
“Anja Niskanen recorded a Finnish rendering of ‘They Don’t Know’ titled ‘Syy On Rakkauden’ for her 1984 eponymous album. The band Death Cab for Cutie often covers ‘They Don’t Know’ in concert; Cutie’s Ben Gibbard recorded an acoustic version of the song for a KEXP-FM live radio broadcast in 2010.”
Tracey Ullman, “They Don’t Know” (1983):
Anja Niskanen, “Syy On Rakkauden” (1984):
Ben Gibbard, “They Don’t Know” live KEXP broadcast (2010):