Carlos Slim continued to build a stake in BT Group, which revealed the Mexican billionaire’s family-owned investment business now holds more than 4 per cent of its voting rights.

In a brief statement, BT noted Control Empresarial de Capitales had upped its holding to 4.3 per cent, building on a 3.2 per cent stake the Mexican business acquired in June for £400 million.

BT’s regulatory filing shows the billionaire’s business hit the 4.3 per cent mark on 29 August, with issuer notification completed yesterday (2 September).

In June, Control Empresarial de Capitales reportedly played down the significance of its stake build, telling Bloomberg it was a monetary decision in line with investments it makes in other companies.

But the move was broadly reported as a validation of new BT CEO Allison Kirkby’s strategy, as the executive looks to rein in costs as part of a broader rejig of the company.

The Mexican company upped its holding barely a fortnight after Indian giant Bharti Global agreed a deal to acquire Altice’s 24.5 per cent stake in the UK-headquartered operator, a move founder Sunil Mittal also played down as purely an investment-driven decision rather than a stealth takeover bid.