British Gas has raised electricity prices by 12.5% and its rivals are likely to follow suit. Another round of inflation-busting increases has put calls for an energy price cap back on the agenda . When then Labour leader Ed Miliband first proposed a cap in 2013 it was dismissed by the Tories as coming from a “ Marxist universe ”. Four years later, Theresa May flirted with the idea ahead of the 2017 election, while Labour included the policy in its manifesto . But whatever it is, it’s not a Marxist idea. For a start, the price cap won’t work because the market is not only broken, it never worked in the first place. Incredibly high start-up costs mean energy is a natural monopoly , in which a small number of companies have been protecting significant investments in fossil fuels and nuclear power since the sector was first privatised. […]