A series of 13 individual films made 1953 and transmitted on NBC Summer 1956 under the title "Detectives Diary." Six were made into two compilations and shown as second cinema features.
An article in Film Review 1953-4 states "a dozen short thrillers have already been made" mentioning that "the first three films" were Ladies of Leisure, Falstaff's Fur Coat, The Thief of London. It states they were made in association with Paramount with George Routledge as the producer. "Script editor is famous Hollywood director Joseph Losey." However they are definitely the first TV series made by Edward and Harry Lee Danziger.

Here's a list of the stories made-
1 The Missing Passenger - starring Patrick Barr and Kay Walsh (probably also known as Ladies of Leisure)
2 Falstaff's Fur Coat - with Howard Marion Crawford
3 The Thief Of London - starring Jack Watling and Gene Anderson
4 Thirty Days to Die (Death) - with Hubert Gregg and Laurence Naismith. Arthur Lowe has a small part
5 The Wedding Gift - starring Hazel Court, Derek Bond with David Horne (a.k.a. Present for the Bride)
6 The Final Twist - with Karel Stepanek and Catherine Finn
7 The Javanese Dagger - with Anthony Nicholls
8 The Ripper Strikes
9 The Wilful Widow
10 The Stranger on the Sea - starring Paul Carpenter and Hugh Latimer
11 The Corpse of Pleasant Avenue
12 The Man who stayed Alive
13 The Sable Scarf - with John Laurie, Andrew Crawford