Look to the Lady by Margery Allingham

The Gyrth Chalice was a priceless historical relic, and it was the duty of the Gyrth family to protect this thousand year old relic of the earliest years of British history. The family kept it in a tower in their estate of Sanctuary. This tower also contained a "secret room", and on his 25th birthday, the Gyrth heir was told of the secret of the "secret room", as he took over the duty of protecting the Chalice.

Percival St. John Wykes Gyrth (Val) was the only son of Colonel Sir Percival Christian St. John Gyrth who was the current protector of the chalice. In just a few days Val Gyrth was due to learn the secret. He, however, was estranged from his father who did not approve of Val's marriage to a woman who had since died. Cut off from funds, Val had fallen on very hard times when he was rescued in London by Albert Campion.

Campion is an amateur detective with a private income. He is described as "a tall thin young man with a pale inoffensive face, and vague eyes behind enormous horn-rimmed spectacles." He was assisted by his man Lugg, an ex-criminal who was very large and muscular.  Campion believed that there was a group of very, very wealthy people who employed criminals to steal very valuable items of such importance that they would never be placed on sale. Campion believed that the Gyrth chalice was the next item on their list to be stolen and offered to assist Val in protecting it.

Campion, Val, and Lugg went to the family home where Campion effected a reunion between Val and his father.  Also present were Val's aunt, Lady Diana Pethwick, who was quite domineering and "difficult". She had the bad taste to be photographed with the Chalice. This photograph had appeared in the newspaper, and had attracted a disreputable group of artistic and new religion types who hung around the neighborhood.  Val's sister Penelope was quite attractive and had a charming personality as did her friend Beth Cairey who was the daughter of an American professor who had taken a house near to the Gyrth's. Another neighbor is Mrs. Dick Shannon who owned a racing stable. She had a bellowing voice and Val called her "One of those damn women-with-a-personality". She wanted to buy horses from the Gryth's, but they did not wish to sell them to her.

Near the Gryth house was Pharisees's clearing which was supposedly haunted by evil spirits, and it was here that Lady Diana died of fright. The doctor believed that she had seen something horrible which caused a heart attack. Lugg went to the clearing, and returned in hysterics.

Campion stopped Penny's attempt to remove the chalice to the safety of a London bank. He took it to an expert in London who testified that the current chalice was a 150 year old copy of the original. Campion now had the problems of not only protecting the chalice from thieves, but also of finding the original chalice to protect. Campion did succeed but his success included confronting the horror of Pharisee's clearing, and a mad cap confrontation between friendly gypsies and the thieves.

This is a great read. Campion is a bit vague about everything. The reader will wonder as the novel goes along how he knew this or that, but all will be explained in the end.  Allingham is one of the great writers of the Golden Age of mystery fiction, and one of my favorite mystery authors.

This book was published in 1931. It is available in paper and e-book form. It is also the first story in the TV production of Campion stories which starred Peter Davison. When the book was published in the United States, the title was The Gryth Challenge Mystery.