Source: Michael Doyle Their Name Liveth For Evermore: The Great War Roll of Honour for Leicestershire and Rutland.
He was the son of William George Waterhouse Reynolds, a corset manufacturer, born 1860 in Belfast, Victoria, Australia and his wife Ida Maud Reynolds (nee Roberts, married on the 16th August 1887 in St. Mary Magdalen Church, Knighton, Leicester), born 1867 in Leicester. William Kingsley was born in the 4th quarter of 1890 in Knighton, Leicester, he had one sibling, Gladys Ruth, born on the 17th September 1888, in Knighton, also residing with the family was William’s paternal grandparents, Thomas Leetham Reynolds, a retired manufacturer, born 1829 in Hull, Yorkshire and his wife Ruth Augusta Reynolds (nee Williams), born on the 18th April 1838 in Hobart, Tasmania, Australia, in April 1891 the family home was at Southlea, Elms Road, Knighton, Leicester. In March 1901 William was residing in the family home at Southlea, Elms Road, Knighton together with his father, a corset manufacturer, his mother and sister Gladys.
William’s Army enlistment documents were not researched, and as such all that is known of his military service is that he was commissioned into the Leicestershire Regiment, and was posted as a 2nd Lieutenant to the 3rd Battalion Leicestershire Regiment he was subsequently attached to the 1st Battalion Leicestershire Regiment and it was to join this unit that he first entered the theatre of war in France on the 15th April 1915. Having joined the 1st Battalion he was allocated to “A” Company. He was awarded the 1914-15 STAR, British War Medal and Victory Medal.
The War Diary records: 10 Sept-15 - 4.35 – 6.35am most intense bombardment of our line, also the 1st KINGS SHROPSHIRE LIGHT INFANTRY on our right, and the RIFLE BRIGADE in FOTWAIR COTTAGE line on our left. Terrific bombardment by guns of all calibres chiefly High Explosive and trench mortars which fired about 50lb and caused fearful damage to trenches. A great deal of shrapnel and High Explosive shrapnel used also especially along our communication trenches. 3 German aeroplanes observing for enemy the whole time, flying right above our trenches. 7.25 – 8.45am another terrific bombardment by same artillery. Bombardment commenced by the 3 German aeroplanes which were flying over our lines suddenly all turning towards the German lines at the same time. Tremendously heavy bombardment again chiefly heavy shells and trench mortars. Points on the bombardment (1) Most intense each time especially High Explosive shells 5 or 6 at a time bursting in or over our trenches. The bombardment was most incessant and is estimated at 2 batteries of heavy guns (about 8 inch), and 2 batteries of 4.5 shells and at least 3 batteries firing shrapnel and High Explosive shrapnel. There were 4 German trench mortars firing and these could be spotted (by the shells) and men were able to run a few bays left or right, thereby escaping destruction. The mortars fired obliquely, they did very great damage partly of “A” Company’s trenches, being absolutely blown in, and great craters and gaps made connection with the right of “A” Company impossible except by a big detour. Their report was most intense. (2) Damage to trenches due by shell fire was also very great and communications trenches in the rear of “A” Company and “C” Company were completely flattened. “B” and “D” Companies also had damage their barbed wire being torn to bits. (3) Casualties are extremely few considering the intensity and length of the bombardment. “A” Company casualties 2nd Lieutenant W. K. REYNOLDS killed (some men had been buried and he dug them out and saved them, and was killed instantaneously almost immediately after) 3 men killed, 7 wounded. “B” Company 3 men wounded (2 very slightly). “C” Company 3 killed. “D” Company 5 wounded. Many men initially buried and buried and rescued and not sent to hospital. Trenches are very good and men got good protection except for direct hits. Casualties “A” Company 1 sick.
On Tuesday September 14th, 1915 The Leicester Daily Post published the following article under the heading. “LEICESTERSHIRE AND THE WAR.” – LOCAL CASUALTIES. – Death of Lieut. W. K. Reynolds. We regret to learn that Mr. Waterhouse Reynolds, of Birstall Holt, on Sunday, received intimation that his only son, Lieut. William Kingsley Reynolds, of the 3rd Leicester’s, had been killed in action in France on September 10. He was 24 years of age, and was home on leave quite recently. Returning to the front on Sunday week, Lieut. Reynolds was in the trenches only five days before meeting his death. He was a very popular officer, held in great respect, and much sympathy will be extended to Mr. and Mrs. Waterhouse Reynolds in the great loss they have sustained.
On Friday September 17th 1915 The Melton Mowbray Times & Vale of Belvoir Gazette published the following article under the heading. “DISTRICT WAR ITEMS.” – BIRSTALL OFFICER KILLED. – Lieut. William Kingsley Reynolds, of the 3rd Battalion Leicestershire Regiment was killed in action in France last Friday. He was the only son of Mr. W. G. W. Reynolds of Birstall Holt. He was 24 years of age, and was gazetted in the regiment about a year ago.

Source: Leicestershire War Memorials Project.
The following information was kindly submitted to the Project in 2015 by S Cope: William Kingsley Reynolds was educated at Rugby School before going up to Merton College, Oxford in 1909. After university he entered Gray's Inn, intending to go to the Bar, but, on the death of an uncle, joined his father in the family firm, Waterhouse, Reynolds & Co., Leicester, and worked with him until the outbreak of war.

He enlisted on 3rd September 1914, and was gazetted to the 6th Battalion, The Leicestershire Regiment in October, subsequently transferring to the 3rd Battalion. He went to Flanders, attached to the 1st Battalion, in April 1915.

On 10th September 1915, when under heavy shell-fire at Wieltje, near Ypres, he went to the assistance of a sergeant who was wounded, and was himself killed by a shell.