I've just gone out to check the belt I can see is moving, but now the car won't start, like the battery has gone flat. Its now on charge so will check again later

Hello, Im new here, I wondered if anyone could help? I have a freelander 1 2.0 td4, drove home from work and parked up as normal last night no problem. Went out this morning, started the car and as I tried to pull away I noticed there was no power steering? ‍♀️ Then noticed the battery light...