Unforgotten theme song: Hidden meaning in the song and title sequence

Unforgotten season four episode one introduced us to victim Matthew Walsh, whose historic murder can be traced back to four living individuals - and as the theme song might suggest, it's up to Cassie and Sunny to "chase" answers.

But what is the name of the Unforgotten title music, and who sings the theme tune?

Unforgotten theme tune: What is the title song and who sings it?

The song that plays during the Unforgotten titles is "All We Do," written and performed by Oh Wonder (songwriting duo Ant West and Josephine Vander Gucht).

The song's opening lyrics ("All we do is hide away") are not only instantly catchy and evocative of the long-running series, but they also arguably reflect the show's premise: that cold case cops Cassie and Sunny make it their mission to solve historic crimes and catch the perpetrators who have long been able to "hide away".

The same goes for the lyric "all we do is lie and wait," which could refer to both the suspects and our crime-solving duo.

Unforgotten season 4 titles: What do the opening credits mean?

The Unforgotten titles (the series of visuals that play alongside the theme tune) are always chock-full of teasers relating to the current season, and this time is no different.

Unforgotten writer Chris Lang previously retweeted a clip showing the season four titles, and said: "Our new titles, full of little teasers and clues."

But what are the teasers and clues this time around? The quick succession of images (including an allotment, test tubes, and an abandoned Sylvanian Family toy in a smashed car) may not seem meaningful now, but several can already be explained.

For example, the first, aerial shot is of Cambridge - and we now that one of the Unforgotten season four suspects, Elizabeth Baildon, lives and works in the Cambridgeshire area, and that her partner works at The University of Cambridge.

There's also a shot of a London scrapyard; and in episode one the headless remains of murder victim Matthew Walsh were found in a scrapyard after being transported in a freezer (where the remains had been kept, frozen, for decades).

We also get a very brief glance at what looks like a print-out of an ultrasound scan - and London-based suspect Ram Sidhu is an expectant father.

Midway through the titles, there's a close-up of a mouth (potentially Matthew Walsh) shouting in anger. But what exactly are they mouthing?

For the latest news and expert tips on getting the best deals this year, take a look at our Black Friday 2021 and Cyber Monday 2021 guides.

Unforgotten theme song: What are the lyrics?

The lyrics we hear during the Unforgotten titles are:
All we do is hide away
All we do is, all we do is hide away
All we do is chase the day
All we do is, all we do is chase the day
All we do is lie and wait
All we do is, all we do is lie and wait
All we do is feel the fade
All we do is, all we do is feel the fade
I've been upside down
I don't wanna be the right way round
Can't find paradise on the ground
I've been upside down
I don't wanna be the right way round
Can't find paradise on the ground.