When is ITV's Unforgotten series 3 on TV?

• Meet the cast of Unforgotten series three
• Who killed Hayley in Unforgotten series three? Meet the suspects
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Here's everything you need to know:

When is Unforgotten coming back to TV?

The six-part drama returned for series three on Sunday 15th July on ITV at 9pm, with new episodes each Sunday.

What is Unforgotten about?

Screenwriter Chris Lang's drama sees the two detectives (played by Nicola Walker and Sanjeev Bhaskar) on a mission to solve decades-old crimes and find justice for the victims.

They come into the picture when human remains are discovered that may be many years old. After identifying the victim, they start to piece together what happened and track down the people who could have been involved, from old friends to family members to lovers. In the process they uncover long-hidden secrets.

In series three, four men are thrown under suspicion for the murder of a girl whose remains are found under the central reservation of the M1 motorway, and it’s up to Cassie and Sunny to figure out whether any of this group of friends had anything to do with her death.

Who stars in Unforgotten series three?

• Unforgotten series 3: FULL CAST LIST

Aside from Walker and Bhaskar, series three puts the spotlight on a "close-knit group of old school friends that have stood by one another through thick and thin."

You may recognise Alex Jennings as King Leopold from Victoria, or the Duke of Windsor from The Crown. He stars as Dr Tim Finch, a successful GP in a country town.

Jennings is joined by Pirates of the Caribbean's Kevin McNally, as James Hollis, a successful media personality with his own quiz show called Sixth Form Sense.

The Vicar Of Dibley's James Fleet appears as the character Chris Lowe, who was initially one of the most successful of the four – running his own advertising company. But his career took a nosedive when he began to suffer from mental health issues, and he now is homeless and living in a camper van.

Neil Morrissey stars as Pete Carr, who he describes as a "sad, bad businessman". After an unsuccessful stint in Hong Kong, he's back in the UK failing to make his fortune as an ISA salesman.

Where is Unforgotten filmed? Where is it set?

The drama starts in London where the remains of Hayley Reid are found at a building site, buried under the central reservation of the M1 motorway.

Hayley disappeared from the fictional little seaside town of Middenham on New Year's Eve 1999, where our suspects were staying at the time in a holiday rental called The Spinney. The majority of the scenes set in Middenham were filmed in Lymington, and we also see some beautiful shots of Middenham estuary.

When Cassie and Sunny's investigations take them to Middenham, they stay in the Angel and Blue pub in Lymington.

In the years since the turn of the millennium, this group of childhood friends has dispersed around the country - so Cassie and Sunny find themselves visiting various towns and cities in the south of England.

Pete Carr's Norfolk scenes are shot in Kings Lynn and Hunstanton. Other filming locations include Harefield House in Uxbridge, Amersham Old Town, Victorian pub The Enterprise in Holborn, Clifton in Bristol and Ealing in London.

The police station and lab scenes are filmed at an empty mansion at Bulstrode Park in Buckinghamshire.

Do you have to see the first two series to understand series three?

Not really! The great thing about Unforgotten is that each series focuses on a different murder case, so there's no backstory required.

What about that series two ending?

Although this is a fresh case for Cassie and Sunny, this is the first time we've seen the duo for the first time since the dramatic events of the series two finale – when they chose to walk away from a case after discovering that their suspects had actually been victims of child sex abuse and worked together to murder their abusers.

Writer Chris Lang previously told RadioTimes.com: "I want to square various circles with Cassie and Sunny... I don’t think it’s something that they will wear lightly."

Before Unforgotten had been recommissioned, he explained: "It’s a secret that they now have and they will have to carry with them through their job and if we do get a third series obviously one will attempt to explore the ramifications of what making such a profound decision will be."

One thing that won't be coming back is any romantic storylines between the two cops. Confirming that Sunny was hoping to kiss Cassie in series two, Lang says: "I’m afraid he was. He got that one horribly wrong. But I think luckily, they’ve recovered from that and they’ve managed to move on... I think that was pretty comprehensively nailed in series two."

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Why is Unforgotten airing in the summer?

It seems unusual for a flagship drama to go out in July and August, traditionally the quiet months for TV drama before the big hitters arrive in the autumn. But perhaps things are changing.

"It is unusual," says Walker. "I think you go two ways with that: you can either think, oh that's unusual, or you think, OK they've got so much confidence in it that they think it's going to be able to handle the summer. I mean, if anything can handle it, I hope Chris Lang's script can.

"And also people watch telly in a totally different way and we've all got to get used to it."

Chris Lang agrees, arguing, "Summer used to – I think - have a connotation. I don’t think it does anymore, is my honest answer. The way we watch TV now is so profoundly different. Plenty of shows have launched in the summer and done very well."

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