Publisher Osprey Group has taken over a Devon firm as it looks to continue the expansion which has seen it double its workforce in the last two years.

Botley-based Osprey has acquired Old House Books, which specialises in producing facsimiles of period maps and reprints of long-neglected publications, for an undisclosed sum.

The move, which will take effect on April 28, follows Osprey’s purchase last year of sci-fi and fantasy publisher Angry Robot.

In 2007 Osprey also bought Shire Publications — which now published a large range of books on all aspects of British heritage and history.

Osprey managing director Rebecca Smart said: “Old House is my ideal addition to the Osprey family. We’ve worked incredibly hard with Shire over the last four years, and with real success, to establish ourselves as a major force in the British heritage market.

“The addition of Old House, especially bearing in mind our plans to grow and diversify its list, will really help to consolidate our position in that sector.”

Edward Allhusen, who founded Old House in 1991, said: “It was always my aim to rescue obscure but fascinating artefacts and texts and to bring them to the audience they deserve, but at this point that audience has grown to the point where to reach it fully requires a publisher with significantly more resources than my own.”

Osprey started in 1970 publishing tea cards that appeared in packets of Brooke Bond tea.

It then begans producing books on military history and moved to Oxford in 1998. Last year it achieved a £7.3m turnover. Two years ago it employed 20 people; now it employs 40.