Margaret Dobson: Publisher who helped set up a thriving list of music books and was chatelaine to the medieval Brancepeth Castle

Dobson: an invalid life awaited her, she was told as a child, thanks to her asthma

Margaret Dobson had two careers: the first in publishing, and the second running a medieval castle in the north of England. That she managed even one was extraordinary as she had been born with asthma. An invalid life awaited her, she was told, and, unless she avoided all exertion, a short one. But she died aged 86 after a life richly fulfilled in ways that no one could have imagined then.

Margaret Green grew up with her younger sister Janet in Cambridge; their father was fellow and tutor in anatomy at Sidney Sussex College. Margaret went to the Perse School for Girls, or rather school came to her, confined to bed as she was. Thus educated at home, she learned to think for herself, and concluded that if life was to be short she had better enjoy it.

She went to Newnham college still disabled, but a new drug, Choledyl, transformed her life. She obtained her degree in English and then, after a secretarial course, took the first job she was offered, as secretary to Dennis Dobson, who had set up as a publisher in London in 1944. Times were hard, with paper still rationed, but the firm survived. She soon found herself at work in the attic office in Park Place, Westminster. Undaunted by the stairs, she enjoyed the erratic progress of Dennis Dobson, the firm and, increasingly, the man. Besides books his other passion was music, and the two coalesced in what became the best musicology list in Britain. Together they ran the firm, taking on new books, supervising the production staff and organising the sales force. They published fiction (some in translation), books imported from the US, and Gerard Hoffnung's musical cartoons – it was diverse, original, and occasionally successful.

Dennis and Margaret married in 1953 and the following year bought a tall, tumble-down house in Church Street, Kensington. The firm occupied the ground floor; above and below their family grew and multiplied. Visitors would find Margaret in bed, feeding the latest baby while correcting proofs, Dennis out hunting supplies at bargain prices or adding to his enormous collection of recorded music. Books, canisters of tape and catering-size tins of soup-powder covered every surface. The children grew up and thrived, used to the cold that kept Margaret's asthma at bay. A constant flow of guests came and went.

The firm was rarely profitable, even with the help of Dennis's family firm (paper-converters in Birmingham), and outside subventions, including a merger with Putnam's. But somehow it survived, and so did its faithful staff, well wrapped up in winter, until 1978, when the lease on the warehouse in Notting Hill Gate fell in, not to be renewed. The need to find space for the back stock of books was urgent. The sales director, tongue in cheek, said that the medieval Brancepeth Castle, near Durham, was up for sale. Margaret went to see it. It had been vastly enlarged by coal money in the 19th century, occupied by the army during the Second World War, then used as a research lab, and had the lead stripped off its roofs by its previous tenant – but it was huge, empty, cold, and cheap.

Providentially, one of Dennis's aunts had left a house in Solihull that sold for enough to buy Brancepeth. The stock was uplifted, 80 Church Street sold, and all was set for firm and family to move north. Dennis went to the 1978 Frankfurt Book Fair; coming back in the train, he had a brain haemorrhage and died, aged 59. Margaret did not turn back. The cold suited her. With children, office, furniture and quantities of books, she moved in.

The books in hand were gradually sold, but eventually the business wound down, and the castle provided a new focus. Making it water-tight, repairing the worst damage, making relics of its palatial past fit for new use, all took time. The ballroom was let for auctions and other events, a whole apartment was fitted inside another grand room, Durham University students settled in others, and the porter's lodge became the village post-office.

As postmistress Margaret became the centre of a widening circle of family, friends and acquaintance. Any good cause was sure of a welcome at the castle. Besides auctions, a twice-yearly craft fair flourishes in the state rooms, weddings and other celebrations elsewhere, and open-air Shakespeare events in the courtyard. Gradual renovation has brought surprises: an abandoned loft in the gatehouse was the army pigeon post office that provided wartime communication with partisans in Norway. St Brandon's church nearby gained greatly from Margaret's enthusiasm; when it burned in 1998, she led the campaign to rebuild it, in different style but fitter for current need.

Margaret Dobson had no time for sentiment, always for feeling. She never wasted time thinking of herself, although constant asthma and the disabilities of age gave her cause enough. But anyone, child, grandchild or acquaintance, in any trouble knew that they could rely on her for help. Never expecting to live so long, she found each new day a miracle, and made it so for everyone she met.

Frances Margaret Dobson, publisher and chatelaine: born Cambridge 9 April 1928; married 1953 Dennis Dobson (died 1959; four sons, three daughters); died Brancepeth, County Durham 19 October 2014.