The first inklings of a cooling of the love affair between investors and big tech may be starting to emerge with a sell off in sector stocks this week. Given how tech occupies a special place in the markets ecosystem, it is a warning that should be taken seriously, not just for bracingly upbeat stock valuations but also the darker corners of the financial system too.

Big tech has assumed a dominant position in global public markets because of a winner-takes-all dynamic that has created a handful of almost unfathomably enormous and successful listed corporate giants, particularly in the US. The frenzy around artificial intelligence over the past couple of years has added lashings of fuel to the fire.

Biggest of the bunch, chips behemoth Nvidia, is now worth $4.3tn, or one-and-a-half times the UK’s entire FTSE 100 index, give or take. This has built a very top-heavy structure in US stock markets, which in turn have swelled to occupy an unusually large chunk of global equities.