If you look at UK debt/GDP ratio over the last 120 years, then is it characterised by sharp increases during economic shocks, followed by stabilisation and decline - usually a couple of years after the crisis has passed. The largest shocks were obviously WW1 and WW2 where debt/GDP ratio reached 187% and 251% respectively. More recently we had smaller peaks following the GFC (82%) and Covid (103%).
https://www.statista.com/statistics/282 ... as-gdp-uk/Whether a government exercises "austerity" or not depends on the budget deficit, not the amount of debt. Running a high deficit means it is stimulating
demand to grow GDP (or so Keynes would have us believe!). I can't find budget deficit data before 1970 but after WW2 I believe there was a high deficit which led to debt/GDP peaking on 1947/48, followed by a large drop as the economy grew.
The post 1970's budget deficit/GDP ratio data shows the two highest peaks in 2009/10 (10%) following the GFC, and in 2020/21 (15%) following the Covid pandemic.
https://commonslibrary.parliament.uk/re ... s/sn06167/The 2010-2019 "austerity years" show the deficit/GDP falling from 10% to 2%, but there was low growth so debt/GDP ratio didn't fall away like it did in the WW1 & WW2 post-war periods. If the government had spent a bit more, it may have grown the economy faster and brought down the debt/GDP ratio, but it didn't, despite this being a period of almost zero interest rates. So I think this is what is meant by "austerity" due to the 2010-19 governments.
FD