Merton was born at 24 Walton Street, Chelsea to Beckwith Smith and his wife, Georgina Butler Moore. His father was on the Stock Exchange.

In 1901, he was at Warren Hill School, Eastbourne from where he went on to Eton. He matriculated in 1909 and at the time of the 1911 census was a Second Lieutenant in the Coldstream Guards at Victoria Barracks.

He fought in the First World War during which he was awarded the D.S.O. the M.C., and in 1917, the Croix de Guerre. He was Mentioned in Dispatches three times.

From: MILITARY OPERATIONS, FRANCE AND BELGIUM 1914 CHAPTER XXI - LAST DAYS ON THE AISNE Compiled by Brigadier-General Sir James E. Edmonds. Edited by Macmillan & Co, 1933

“On the front of the 1/Coldstream, just east of the Troyon factory road, the Germans had run out a sap, and it was decided to fill it in. At 8 P.M. a platoon of the battalion, led by 2/Lieut. M. Beckwith Smith (who was wounded and subsequently received the D.S.O.), crossing the hundred yards of No Man's Land, rushed the trench with the bayonet) Artillery activity continued on both sides: the Germans occasionally managed by lucky shots to burst shells in the billets of British units well south of the river; the 9th Lancers in this way lost over forty officers and men at Longueval (2 1/2 miles south of Bourg) on the 29th.”

On 14 March 1918, he married at St. George’s, Hanover Square, Honor Dorothy Leigh. They had four children. [One of his granddaughters was Lady-in-Waiting to Diana, Princess of Wales.]

In 1931, he inherited The Manor House, Stratton Audley from his father-in-law. They lived, also, at Aberarder, Strathnairn, Inverness-shire.

He transferred to the Welsh Guards in 1930 and served with them until 1938 when he took over command of the Lahore Brigade Area 1938-1939.

He commanded the 1st Guards Brigade in France in 1940 and during the retreat to Dunkirk told his fellow officers, ‘We have been given the supreme honour of being the rearguard at Dunkirk. Go and tell your platoons the good news!’

He was a jolly man known as ‘Becky ’ and briefed his men how to shoot the Stukas that were strafing and bombing the area. ‘Stand up to them. Shoot at them with a Bren gun from the shoulder. Take them like a high pheasant. Give them plenty of lead. £5 to any man who brings one down.’ [He was perhaps overlooking the fact that few of the rankers would have had any experience of the aristocratic sport of pheasant shooting.]

After the retreat from Dunkirk, he was given command of the territorial 18th East Anglian Infantry Division which he trained in preparation for duty overseas.

In early 1942, after many weeks at sea, the division was landed at Singapore. The Japanese forces invaded the island on February 8th. Because of the defensive strategy implemented by the Allied commander, General Percival, most of the 18th Division saw little or no action.  Percival surrendered the 80,000 British Commonwealth troops at Singapore on 15 February. In August 1942, Merton was moved to Formosa (now Taiwan) along with all the senior officers from Singapore.

Before leaving Merton Beckwith-Smith sent this message:-
"On my departure for Japan I wish to take what may be my last chance to thank all ranks of the 18th Division for their cheerful service and loyal support on many shores and seas during the two years I have had the honour to command the Division.
I regret I have been unable to lead you to the success in battle to which your cause and sacrifice is entitled, and although I leave you with a heavy heart, I carry with me many precious memories and a sense of comradeship such as could only have been inspired by the trials and disappointments which we have shared in the last few months.
Difficult days may still be ahead, but I know that the spirit which today animates all ranks of the Division will prevail and will form the corner-stone on which one day a just and lasting peace will be found.
God grant that day may not be long delayed and that we may soon meet again.
Meanwhile GOOD LUCK, HEADS UP, KEEP SMILING.
(Sgd.) M. BECKWITH-SMITH Major General. 18th August 1942”
He died on 11 November 1942 at Karenko Camp, of diphtheria.

In the spring of 1946, the Imperial War Graves Commission exhumed all the Taiwan POW remains and re-buried them in the Sai Wan Bay War Cemetery in Hong Kong. His plot is V H 1.

He is also commemorated on the war memorial at Daviot, Inverness-shire and by a metal plaque on the wall of St Paul’s Episcopal Church, Strathnairn.

"To the Glory of God and in Proud and Loving Memory of

Maj. Gen. Merton Beckwith-Smith, DSO, MC, of Aberarder,

Coldstream Guards 1910 -1930 
Commander 1st Guards Brigade 1939 - 1940
Commander 18th Division 1940

Born 11 July 1890
Died 11 November 1942 a prisoner of war in the Far East

The Beloved Husband of Honor Beckwith-Smith

"And so it befell that when the hour of trial came, these men gave an example of courage and devotion the memory of which will never perish ".