Landlord not responding about deposit. Can I get this back?

Located in England.

For context, my old landlord (in nice words) loves to dodge any and all communication he can and has broken the law several times, so I fully expect him to be dodgy and keep my whole deposit. Our flat had serious maintenance issues which he just fails to address or fix (written in contract it is his responsibility for maintenance unless it’s light bulbs, not mine). Our landlord is most definitely inexperienced and should not have the responsibility he does. This context just shows how little faith I have that he’ll return our deposit.

Our deposit is protected with mydeposits and is valued at £980

I moved out my last flat on June 30th this year, and we handed the keys directly back to the landlord who was at the property. I have an image taken to prove i left the keys where he told us (the front gas box?) and I saw him collect the keys right after. He didn’t even inspect the flat he just stormed off. Bear in mind the day before he threatened to take the deposit if we left the house in a bad state (it has a serious mould problem that was there when we arrived and was never addressed, tap degraded to unusable despite numerous attempts to tell him otherwise, non functional smoke detector, walls damage etc), and I explicitly told him that the problems in the flat were there on arrival, and he would know this if he just scrolled up in the text chat.

On Friday (July 4th, 4 days later), I messaged him asking either to give us our deposit back or tell me if he’s going to file any deductions. No response.

My current thinking is he has 10 days from when we hand the keys back to give us our deposit or file deductions, however I don’t know for sure.

Can you help me with what to do if I get no response or if he tries to claim the entire deposit with bs? Thanks.