The largest of the four positions is a £17m holding in semiconductor business Spin Transfer Technologies. The company is a subsidiary of Allied Minds, the technology firm which is itself Woodford’s 11th largest holding at 2.4 per cent of his portfolio.

The three other positions are in a trio of healthcare companies: Emba, Viamet, and Stratified Medical.

Following the purchase of these new positions, the fund now has just over 5 pe cent of its assets in unlisted companies.

“We are very excited about the long-term growth potential this part of the portfolio represents,” said Stephen Lamacraft, a fund manager at Woodford Investment Management.

The manager also added a position in engineering outsourcer Babcock International during the market volatility in October – a month which saw the FTSE All Share fall as much as 11.6 per cent below its September peak before recovering sharply.

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“We have been attracted to the business for some time and have been patiently waiting for an entry point. Over the course of this year, the shares have fallen from £13 in late February to trade as low as £10 briefly in the last few weeks,” Lamacraft said.

Lamacraft said the team was also “surprised” to see Rolls-Royce shares sell off so aggressively following the manufacturer’s profit warning; Woodford used the falls to top up his position in the company, which now accounts for 3.1 per cent of his portfolio.