Ritchie’s found two tables from HMRC. Then he says:
First, we are not being overtaxed at present. In fact, it is fairly obvious that the economy’s capacity to pay tax is not being exploited, despite the deficit.
Umm, yeah. Try adding the £150 billion or so (a further 33% of the amount HMRC collects, a further 10% of GDP) in tax that is raised by people other than HMRC before making that claim, maybe?