Writer, 51, was last seen walking her dog near her home in Royston, Hertfordshire, a week ago

Police are becoming increasingly concerned for the welfare of a popular children’s author who has been missing for more than a week.

Helen Bailey, 51, was last seen at about 2.45pm on 11 April near her home in Royston, Hertfordshire, where she was walking her dog, a miniature dachshund.

Police have appealed for help tracing the author, who is described as slim with long black hair. It is not known what she was wearing at the time she went missing.

Bailey has written and published a number of books for teenage girls, and is best known for a successful series of novels about the fictional character Electra Brown – a girl who turns to her best friends for help when her family begins to fall apart.

She is also the author of a popular blog called Planet Grief, which she began after her husband of 22 years, John Sinfield, drowned while the couple were on holiday in Barbados in 2011.

In the blog, Bailey attempted to come to terms with her husband’s death. She wrote: “Believe me, I know what it’s like to feel the unrelenting pain of searing grief, to long to spontaneously combust in front of the meal-for-one section in M&S, to stand in the park and scream into the sky: ‘Where are you?’ and to sob hysterically over having to drag a slug-covered wheelie bin into the street, alone, late at night, week after lonely week.”

Bailey retold the story of how she persuaded her “equally workaholic” husband that they needed a break, after which they travelled to the Caribbean island on which they had married. Days later, she watched as he was dragged out to sea and drowned.

“On the 27th February 2011, whilst on holiday in Barbados, my husband got off his sun lounger, adjusted his glasses and headed into the sea for a swim,” she wrote.

“Moments later, I heard him call for help, and watched helplessly from the beach as he was pulled out to sea by a rip tide. He drowned. Bizarrely, after he died, almost the first thing I said was, ‘But I’m wearing a bikini!’ as if bad things can’t happen when you’re wearing a good bikini. But they can, and it did. At the age of 46, I crash-landed on Planet Grief, a place where nothing, not even my own reflection in the mirror, felt familiar.”

Bailey was born in Newcastle upon Tyne and grew up in Ponteland, Northumberland. After obtaining a degree in science, she worked in the media and now runs a successful London-based character licensing agency handling properties such as Snoopy, Felicity Wishes, Dilbert and Zorro.

Since 2013 she has lived in Royston, Hertfordshire, with her new partner – whom she refers to as “Gorgeous Grey Haired Widower” – and his two sons.

Her blog was turned into a book called When Bad Things Happen in Good Bikinis, published last October.

A spokesman for Hertfordshire police said: “Police are appealing for the public’s help to trace a woman who has gone missing from Royston.

“Helen Bailey, aged 51, was last seen at around 2.45pm on Monday, April 11. Concerns are growing for her welfare and police are urging Helen to make contact to let them know she is safe and well.”

Herts Police (@HertsPolice) Have you seen missing Royston woman Helen Bailey? Call police on 101. https://t.co/5LENaMkDIk pic.twitter.com/qy7fZznxTp

Hachette Children’s Group, which owns Hodder Children’s Books, Bailey’s publisher, told the Bookseller magazine: “Along with Helen’s friends and family we anxiously await the news of her safe return.”

Bailey is said to have connections to Kent, London and around her home village of Ponteland. Anyone with information is urged to call the police non-emergency number 101.

The appeal for information on Bailey fwas issued as the same force said in a separate statement that it was seeking help from the public to trace another woman who went missing, Natalya Shieff.

Shieff, whose disappearance appears to be unconnected to that of Bailey, was last seen at the Fit4less gym in Hatfield, at around 1pm on Sunday. She is described as being around 5ft 5in tall, of thin build, with dark brown shoulder length hair, and was last seen wearing a baggy jacket, pink sports top, multi-coloured trainers, dark grey jogging bottoms and a red Arsenal woolly hat.

A Linkedin Profile for Shieff said that she was a writer and volunteered at a literacy charity that supports volunteers working in primary schools with children.