The chief executive of the Synchronica mobile messaging company bought 800,000 shares in the business three weeks after it received a takeover approach that it had not revealed to the market.

Angus Dent spent £490,000 on the shares on November 30 at 6.125p each. The shares have since doubled to 12.4p largely as a result of an approach from rival Myriad regarding a possible takeover. Synchronica issued that statement on January 3.

However, the offer document posted on the website of Myriad, a Swiss company, shows that it first approached its British rival on November 10.

Mr Dent told The Times that the two businesses had met earlier in 2011 at the company’s offices in Tunbridge Wells. He said that the company then received a letter in early November that constituted “a vague approach” that was firmly rebuffed.

Mr Dent said that he assumed the approach had gone cold when he moved to buy shares and that he cleared the stock purchase with the company’s nominated adviser Northland Capital Partners, which told Mr Dent to check with executive chairman David Mason before acting. “We had a five to ten minute chat and agreed it would be appropriate,” Mr Dent said.

However, Myriad came back two days later with a fresh offer. “We thought Myriad had come on another fishing expedition,” he said. Yet Myriad’s interest proved genuine as it made a £20.6 million offer, which it revealed in what Mr Dent described as a “rather silly announcement”.

Synchronica has repeatedly urged its shareholders to reject its Swiss rival on the basis that the offer undervalued the shares of the British company. Mr Dent defended his stock purchase. “You can only act on what you know at the time,” he said. He bought the stock because he believed that the company was “massively undervalued” and that its shares have historically risen toward the end of the year.

Synchronica experienced a turbulent 2011. FinnCap, its nominated adviser, decided to step back from offering advice to the company earlier in the year. Then its co-founders Carsten Brinkschulte and Nicole Meissner, respectively chief executive and chief operating officer, quit the company in September.

Myriad continued with its discussions with the board of Synchronica from 18 November 2011 up to and beyond the announcement of 3 January 2012 which detailed that Myriad and Synchronica were “in talks”.

Myriad asks the independent directors of Synchronica (being those not involved with conducting or authorising the share purchase) to consider:

i) whether there has been a breach of fiduciary duties by those directors involved; and

ii) whether those directors should resign with immediate effect.

Myriad also questions what information the company’s Nomad, Northland Capital Partners, received to approve this share purchase and as to why it was not viewed as insider trading.