Elsie Knocker, later Baroness de T'Serclaes, MM, OStJ (née Elizabeth Blackall Shapter; 29 July 1884 – 26 April 1978) was a British nurse and ambulance driver in World War I who, together with her friend Mairi Chisholm, won numerous medals for bravery and for saving the lives of thousands of soldiers on the Western Front in Belgium.

She was subsequently adopted by Lewis Edward Upcott, a teacher at Marlborough College, and his wife Emily who sent her to be educated at St. Nicholas's, Folkestone, and then at the exclusive Château Lutry in Switzerland.

When war was declared in 1914, Knocker wrote to her friend and fellow motorcycle fanatic, Mairi Chisholm, that there was "work to be done",[3] and suggested they go to London to become dispatch riders for the Women's Emergency Corps.

"[6] In the early evening of 25 September 1914, Knocker, Chisholm and the other volunteers (which included Lady Dorothie Feilding and May Sinclair) followed Dr. Munro down the gang-plank of the S.S. Princess Clementine at Ostend, West Flanders.

[4] While visiting the town of Nazareth (8 miles south-west of Ghent where the corps was initially quartered) Knocker was witness to the aftermath of a massacre when she came across 26 Belgian military policemen who had been shot and mutilated by the Germans.

[3] At the end of October, the corps relocated to Furnes in unoccupied Belgium, near Dunkirk, where the women worked tirelessly picking up wounded soldiers mid-way from the front and bringing them back to their field hospital at the rear.

In November, the two decided to leave the corps and set up their own dressing station five miles east in a town named Pervyse, north of Ypres,[3] just one hundred yards from the trenches.

[9] In January 1915, they were rewarded for their courageous work on the front lines when they were both decorated by King Albert I of Belgium with the Order of Léopold II, Knights Cross (with palm).

[10] In January 1916, Knocker was married again, to Baron Harold de T'Serclaes, a pilot in the Belgian Flying Corps, and a devout Roman Catholic.

After she and Chisholm rescued a wounded German pilot in No Man's Land both women were awarded the British Military Medal, and were made Officers of the Most Venerable Order of St. John of Jerusalem.

[4] In 1939, at the outbreak of World War II, the Baroness joined the Women's Auxiliary Air Force (WAAF) as an Aircraftwoman 2nd class, becoming an officer in February 1940.

She was greatly concerned about the welfare of both animals and the conservation of Ashtead Common where she could often be seen walking her pets, "flamboyantly dressed with large earrings and a voluminous dark cloak".