Viewers will know that Gary has been hooking up with Olivia pretty much all of this series of Ex On The Beach, so you can imagine her face when she then sees him locking lips with ex-girlfriend Lillie - especially after confessing he had cheated on her for a second time...
MTV had teased that Lillie and Gaz end up in bed together, but what we didn't know is that Olivia walks in on the pair as they're kissing.
It may be dark in the bedroom, but there is no mistaking Lillie and Gaz necking on. Olivia goes into the bedroom to get into the bed next to the former flames, before thinking twice after realising what is happening right next to her.
She makes a quick exit, and, a little in shock (as we all are) Olivia tells the camera: "Oh my god."
Noticing someone leaving the room, Gaz shouts up to Conor Scurlock and asks him who it was, he replies Olivia and Gaz and Lillie can't help but laugh at the (slightly awkward) situation.
Is there ever a quiet night in that villa?!?!
Ex On The Beach 509 | WTF! Lillie And Gaz Neck On
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Gaz and Lillie's kiss comes surprisingly after Gary confessed he had cheated on Lillie a second time. His admission came following the arrival of Melissa Reeves. Fans may recognise Melissa from series two of Ex On The Beach - Gaz had surprised her on the show as her ex.
Well, she's back to return the favour and Gaz admits to Lillie, Melissa is one of the girls he had slept with behind her back when they were dating. He then reveals that Lillie had actually met Melissa after it happened, prompting Lillie to say: "So she was all nice to my face, knowing that she slept with my boyfriend."
Of course, conversation turns to Melissa and Gary sleeping together when she arrives at the villa for the first time. When asked if she owes Lillie an apology, Mel fires back that she "isn't sorry" as it "wasn't her fault." She is single and Gary was the one in a relationship.
Her comments cause Lillie to break down in tears and of all people to comfort her, Gaz steps up to the plate. He promises "not to leave Lillie's side" and continuously apologises to her for having hurt her.
Gaz tells Lillie: "You are the best person I have ever met in my whole entire life Lil, and you will make someone very f**king happy. You are literally like wifey material. I am so, so sorry."
And while, naturally, Lillie says she "hates" Gaz, she admits she has nobody in the villa to turn to: "I hate Gary, but he's the only person I really know."
Gaz previously admitted to cheating on Lillie with Chrysten Zenoni during a trip to Australia. Initially, Gaz denied that he had been unfaithful to Lillie when questioned by her, but he was caught out when Chrysten later revealed she and Gaz had slept together while he was with Lillie.
At the time, Lillie said hearing Gaz had cheated "completely killed her."
She said: "It was sad when we broke up and it was hard to see him again, it was hard to have a chat with him about our relationship, but to then find out he cheated on me and I had no idea just completely changes all my thoughts and memories on our relationship and just the way I feel about him now. It completely killed me."
Lillie had appeared to move on from Gaz with Stephen Bear, but was dealt another blow on learning that Bear had actually been kissing Chrysten behind her back in the villa.
Can the girl not catch a break?!
Ex On The Beach continues Tuesday 11 October at 10pm on MTV.
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