The expanded stake, worth around £458million, tightens the tycoon’s grip on the company as its largest shareholder and comes after Business Secretary Grant Shapps cleared the way for Kretinsky to increase his control of IDS following a review under the National Security and Investment Act.

It will fuel speculation over the 47-year-old’s intentions and the future of Royal Mail.

The group is under pressure as losses stack up, postal workers strike and letters and parcels go undelivered.

The move takes Vesa’s holding closer to the 30 per cent threshold which under City rules would require it to make a takeover bid for the entire business.

Victoria Scholar, head of investment at Interactive Investors, said that given the 60 per cent slump in the IDS share price this year, Kretinsky – known in City circles as the Czech Sphinx for his poker-faced approach to investment – could be ‘acting opportunistically’ to snap up the stock at a ‘significant discount’.

The likelihood of a swoop appears to be growing each day, she said, saying IDS ‘could be ripe for a takeover’.

But despite its woes, the possibility of Kretinsky taking over IDS is likely to unnerve many due to concerns the tycoon could split off the troublesome UK business, leaving him in control of the much-more successful GLS.