January was a turbulent month for investors with markets tumbling across the globe amid concerns of slowing economic growth in China and the falling oil price.

During the month, Woodford sold the remainder of his shares in FTSE 100-listed Royal Mail, a position he had started to reduce in December.

In an update to investors, he said: “This is still an attractively valued business, in our view, but we are increasingly concerned about the regulatory environment and the ability of the company’s management team to retain the benefits of cost rationalisation and potential property disposals for its shareholders, rather than for other stakeholders such as staff and pensioners.

“We therefore sold the holding in favour of other opportunities in which we have more confidence and where share prices have become increasingly attractive in recent weeks.”

The disposal of Royal Mail allowed Woodford to add to holdings in the US biotechnology sector, including AbbVie, Prothena, Alkermes and Theravance Biopharma.

He also added to Next, G4S, Legal and General, Provident Financial and NewRiver Retail.

In the update, he highlighted the “robust performance” of tobacco firm Reynolds American.

He said: “Its shares had ended a strong 2015 on an uncharacteristically weak note, but they rallied in January as the market’s bout of nervousness underscored the company’s dependable characteristics once again.”

He noted that the tobacco sector as a whole “performed well”, with shares in Imperial Tobacco  and Reynolds American ending the month at all-time highs, and British American Tobacco “not far off its own highest close”.

On his outlook for markets, Woodford said “we remain cautious on the global economic outlook and continue to see a difficult year ahead for risk assets”.

The fund was a top decile performer in 2015, returning 16 per cent, compared to a sector average of 6 per cent.