[2] MacColl's "They Don't Know" reached number two on the Music Week airplay chart[5] without generating sufficient sales to reach the UK Singles Chart - a shortfall blamed on a strike at the distributors for Stiff Records keeping the single out of stores, although its producer Liam Sternberg attributes the failure of "They Don't Know" to ill feeling which developed between MacColl and Stiff Records president Dave Robinson: Kirsty and Dave didn’t get along ... She didn’t want to sign a longer deal, so Dave didn’t promote the record.

I mean, I wore that pink lurex miniskirt for weeks, with all the dry ice on flipping Top of the Pops, & I still didn't make it.

[11] The production of Ullman's "They Don't Know" was credited to Peter Collins, Waterman's Loose Ends partner.

Waterman honed the track, including having MacColl and Rosemary Robinson (the wife of Stiff Records president Dave Robinson) "add Shangri-La-type backing vocals", in Waterman's words, and having MacColl reprise her original "bay-bee” to intro the third verse (as Ullman had a limited high-end range).

Although she had three more entries in the UK Top 30 - including the top-10 hit "Move Over Darling" - Ullman, when asked in a 2017 The Guardian interview "If you could edit your past, what would you change?

"[14] In 1997, "They Don't Know" became the theme song for the final three seasons of Ullman's HBO television series Tracey Takes On....

[15] Ullman sang the song in 2002 at a memorial tribute concert for MacColl, who was killed in a boating accident in December 2000.

Comparing the two versions, Ken Tucker of The Philadelphia Inquirer wrote "Ullman's rendition...makes [the song] palatable to American audiences by [replacing] McColl's fervent intensity with a bouncy cheerfulness & layers of...synthesizers...It's a cheerful throwback to the innocent hits of 1960s girl-group rock".

Directed by Stiff Records president Dave Robinson, the video for "They Don't Know" had a storyline devised by Ullman herself in which she played a young woman in a blossoming romantic relationship with her working class, ne'er do well boyfriend in the 1960s.

The video concludes with Ullman portraying the song's protagonist as a dowdy council estate type mother (not unlike her character Betty Tomlinson from the comedy sketch show Three of a Kind), unkempt, heavily pregnant and shopping for groceries in her slippers, her life of domestic drudgery sustained only by her fantasy of being in a relationship with her idol Paul McCartney.