Gillian Bradshaw

 Gillian Bradshaw is a popular novelist... who has been writing since around 1980.  I came across her first works, an Arthurian Trilogy, which was set in Dark Age Britain.  The three novels cover the development of an Arthurian Kingdom... and the arrival of Gwalchmai, Arthur's nephew, from the Orkney Islands... The final work, In Winter's Shadow is narrated by Gwynhwyfar, (Guenevere) who relates her romance with Bedwyr and the fall of Camelot....

Gillian was born in the USA and reared partly in Chile.. She studied Classics and accumulated a store of knowledge about the ancient world.  Many of her novels after the Arthurian work were set in Classical Rome and Greece and Britain. One follows the life of Archimedes, engineer, mathematician and physicist. 

She also writes about women in the classical world.. who take on male roles such as learning about doctoring. Another novel is based on the idea that Caesarion, the son of Cleopatra, survived  (when he was meant to be executed) and manages to lead a new life....

She married a British physicist and lives in the UK... and has written several science fiction novels.. using her knowledge of scientific research. 

One of her best novels is "Island of Ghosts" which is set in Roman Britain...It is based on the arrival of some Sarmatian soldiers who have been defeated by the Romans and offered exile in Britain..which was at the very edge of the Roman Empire (hence the title Island of Ghosts as they were all in effect "dead" to their former life)

The hero of the book is  Ariantes, their leader, who learns about life in Britain, learns about Roman skills such as literacy, and settles down breeding horses... with a British wife.... The Sarmatian soldiers who were skilled in fighting and breeding horses, may well be one of the events that inspired the story of King Arthur and his knights....This connexion may be a reason for Bradshaw deciding to write a story based on their coming to Britain. 

She has also written novels set in Puritan London... but my favourite is "Island of Ghosts"....