Andy Burnham’s arrival has prompted some dramatic warnings about the future of British capitalism.The ever-excitable headline writers at the Daily Express declared UK stocks were in “free fall” after his cabinet appointments, a somewhat alarming description of a market that slipped 0.7 per cent.Meanwhile, one Telegraph columnist moved beyond markets into something closer to dystopia, warning that Burnham’s “monstrous alter ego, currently repressed, is that of a revolutionary socialist committed to obliterating conservative Britain”.Elsewhere, we got the usual guessing game, with headlines like “FTSE 100 stocks to watch under an Andy Burnham government”, “FTSE 100 reacts well to Burnham’s first moves”, “Hedge funds circle UK stocks”, and so on. Mildly bullish forecasts, mildly bearish warnings, confident predictions about which stocks might benefit or be buffeted by a new government – the usual political stock market ritual.Worrying about bond yields is one thing, given Burnham’s previous comments about not being “in hock” to bond markets. However, divining future FTSE winners and losers from political tea leaves is another matter entirely.Firstly, the FTSE 100 is hardly a proxy for the UK, with many of its biggest companies earning most revenues abroad.Secondly, a study of 24 stock markets and 173 governments found no clear difference in returns under left- or right-leaning administrations, concluding that political investment strategies are “likely to be futile”.Thirdly, if politics dictated markets, clean-energy stocks should have thrived under Joe Biden and struggled under Donald Trump. They didn’t: green indices tanked under Biden and soared under Trump.Burnham’s political identity has proved hard to categorise: hence, the joke about a Blairite, a Brownite and a Corbynite walking into a bar, only for the bartender to ask: “What’ll it be, Andy?” However, even a clearer label would not help investors predict stock returns.