AITA for refusing to pay rent after my roommate moved out and the landlord tried to use my security deposit to cover the loss

I (M26) rented a two-bedroom apartment with a homeless friend of a friend (M29) for a year from February 2023 to February 2024. The landlord asked us to move out before our lease expired at the end of January 2024 because the owners wanted to sell the property, and he was trying to avoid the extra month of commission to the agent. I told him I needed to find a new place before moving out, and he understood. My roommate was supposed to be moving to a 1-bedroom apartment with a friend, but they had to wait until the neighbor moved out in April. When they offered to renew our lease, I told them I was moving on (I had found a new apartment), but my roommate was happy to stay as long as he wanted. They offered him a 6-month lease, which he signed, but he did not pay his share of the deposit, because neither of us got our deposit back (and we didn't have it). I moved out, and he stayed, with a promise to pay back the deposit as soon as he got his tax return. There was no problem renting the new place without the deposit, as I was subletting a furnished apartment, and the agent didn't care about the deposit.<br><br>He didn't pay his share of the deposit, and he didn't pay his share of the rent for the whole time he stayed. I told him multiple times I wouldn't pay the rent, as we were no longer flatmates. He insisted on staying at the place, even though he could stay with his friends for free. I told him I didn't care as long as I wasn't paying the rent. However, my name was on the contract, and I was responsible for paying the rent. In March, I received a letter from the landlord reminding me to pay the rent, and I told him I wasn't paying because I didn't live there anymore. He told me I had to honor the contract, and I should pay it from February until he found a new tenant or my roommate left. I told him it wasn't my problem. In May, he tried to use my deposit to cover the loss in rent, as he had already given my roommate an eviction notice. He said he would give me back whatever was left of the deposit, and I told him I wouldn't accept it, because I was owed a full deposit, and I had to get at least that. He told me he couldn't pay me a full deposit back, because he had to cover the loss of rent, and I told him to pay me the full deposit, or I would sue him. He's been telling me I should pay the rent, and the case will go to court, but I'm waiting for my deposit. Do I have a case? AITA?<br><br>&#x200B;<br><br>Update: After the landlord e-mailed me stating that he would pay me the full deposit, I told him I wanted to discuss it before accepting it. I wanted to know the amount and the date it was deposited in my bank account. He sent me an e-mail stating that the deposit was £900, and he would deposit it on Friday. I replied to the e-mail saying that the deposit was £1040 (which I could prove with the signed contract), and I wanted it on Wednesday. He replied saying that he would deposit the remaining £140 in addition to the remaining £900 on Monday. Now I'm waiting for the deposit to be transferred to my account.