Downie told Press Association Sport: "It was a fight for me out there because I was always second, but I knew when I saw her floor score come in that I had done better than that in qualification.
"Obviously I was aware of where I was standing throughout but I tried to ignore her scores and just focus on myself. It was just crazy when I discovered I'd won and I don't think it will sink in for a while.
"I've definitely surprised myself in the last couple of weeks. I had to have two weeks off after the British Championships because I had to rest my foot, so to come out here and win gold is amazing really."
Downie will now turn her attention to the individual finals this weekend, where she will compete in floor and vault as well as being joined by her older sister Becky in beam and bars.
Downie, who won European all-around bronze in 2015 when she was just 15, added: "My main target was the all-around and I just wanted to do better than I had done two years ago.
"To be honest I wasn't expecting to be European champion. I was happy to take any medal that came my way but the gold is just amazing. Now I can go into the finals with a chance of more medals and enjoy competing with Becky."
Hall's medal also came in dramatic fashion as he completed a risky high bar routine on his final piece of apparatus to narrowly keep Russia's Nikita Ignatyev at bay.
Afterwards Hall, who also has the individual high bar final to come, admitted he had sometimes doubted his ability to medal at a major championships after a series of near-misses on team selection.
Hall said: "It's hard to admit that this medal has not always been a prospect. I've failed to make the team so many times that I've been left wondering how hard I have to work to make it.
"But in the past few months I've really started to believe in myself and what the guys achieved in Rio really motivated me 100 per cent. I've justified that by coming away with a bronze medal."
