Government debt ballooned in 2010-2012 (the so called Great Recession due to the depth and lack of the recovery), was largely stagnant until 2020 when it again went up again (covid). These two events moved debt as a ratio to GDP from around 40% pre financial crisis to 80% post crisis (for reference was 65% when the coalition took power) - then to 97.5% in with covid. Believe it or not neither of these increases were down to government policy - there is an argument that the response to this deep recession was the wrong one (austerity) and inhibited growth which by default reduces the debt/GDP ratio however the evidence is weak with evidence supporting that not following these measures will have had the exact opposite effects and made matters worse. People tend to decide which was the right approach based on their political leanings on economics rather than being able to conclude without dispute the better approach. All we know is what was done and happened.
Anyway enough ramblings from me, you inferred you see it’s as purely political policies taken by the government so specifically which government policies in this period are you referring to as being anywhere near as impactful as the financial crisis (and resultant recession) and Covid?