Question: George Boscawen, 9th Viscount Falmouth is a former officer in which regiment of the British Army ?

Context paragraphs:
George Boscawen, 9th Viscount Falmouth: George Hugh Boscawen, 9th Viscount Falmouth, DL (born 31 October 1919) is a Cornish peer and landowner.  His subsidiary titles include Baron Le Despencer (created 1264) and Baron Boscawen-Rose.  A former officer in the Coldstream Guards, he was Lord Lieutenant of Cornwall from 1977 to 1994.

Lady Mary FitzWilliam: Lady Mary Wentworth-Fitzwilliam (1851–1921) was the daughter of William Wentworth-FitzWilliam, 6th Earl FitzWilliam and of Lady Frances Harriet Douglas.  On May 23, 1872 she married the Hon. Hugh Le Despencer Boscawen (1849–1908), son of Evelyn Boscawen, 6th Viscount Falmouth (1819–1889).

George Boscawen, 3rd Viscount Falmouth: George Boscawen, 3rd Viscount Falmouth, PC (6 May 1758 – 11 February 1808), was a British army officer and statesman of the late 18th and early 19th centuries.  His career included service as Captain of the Honourable Corps of Gentlemen-at-Arms during the reign of George III.

Sir Cecil Bishopp, 6th Baronet: Sir Cecil Bishopp, 6th Baronet (30 October 1700 – 15 June 1778), later Bisshopp, was a British politician.  He succeeded to the title of 6th Baronet Bishopp, of Parham, co.  Sussex on 25 October 1725.  He was Member of Parliament for Penryn between 1727 and 1734, having been returned unopposed on the interest of the Boscawen family into which he had married.  He also represented Boroughbridge between 1755 and 1768.  He married Hon. Anne Boscawen, daughter of Hugh Boscawen, 1st Viscount Falmouth and Charlotte Godfrey, in 1726.  In addition to Parham Park, Sussex he was also the owner of a house at 11 Berkeley Square, London which Horace Walpole purchased from Bisshopp's heirs in 1779 and in which Walpole lived until he died there in 1797.  Sir Cecil died on 15 June 1778 at the age of 77.

Earl of Falmouth: The title of Earl of Falmouth has been created twice, once in the Peerage of England and the second time in the Peerage of the United Kingdom.  The first creation, on 17 March 1664, was for Charles Berkeley, 1st Viscount Fitzhardinge, who was at the same time created Baron Botetourt of Langport.  It became extinct upon his death the following year.  The second creation, on 14 July 1821, was for Edward Boscawen, 4th Viscount Falmouth.  It became extinct in 1852.

Coldstream Guards: The Coldstream Guards (COLDM GDS) is a part of the Guards Division, Foot Guards regiments of the British Army.

George Boscawen (British Army officer, born 1712): Lieutenant-General George Boscawen (1 December 1712 – 3 May 1775) was a British Army officer and politician, the fourth son of Hugh Boscawen, 1st Viscount Falmouth.

Quintessence (horse): Quintessence (1900–1917) was a British Thoroughbred racehorse who won the 1000 Guineas of 1903 and was unbeaten in her six races.  She was owned and bred by Evelyn Edward Thomas Boscawen, 7th Viscount Falmouth.  After retiring from racing she became a successful broodmare, with her son Clarissimus winning the 2000 Guineas.

Evelyn Boscawen, 7th Viscount Falmouth: Major General Evelyn Edward Thomas Boscawen, 7th Viscount Falmouth, (24 July 1847 – 1 October 1918) was a British peer and British Army officer.

Lionel Petre, 16th Baron Petre: Captain Lionel George Carroll, 16th Baron Petre (3 November 1890 – 30 September 1915) was an English peer.  He was educated at the Oratory, Edgbaston & Sandhurst.  There is a story that he originally intended to join the King's Royal Rifle Corps but was turned down he then joined the fourth Pioneer Battalion, Coldstream Guards.  He became a lieutenant and finally a captain.  In 1908, he became engaged to Catherine Margaret Boscawen (1891-1983), granddaughter of the 6th Viscount Falmouth, taking a diamond from an earring of the Petre jewels to make the ring.  They married at Westminster Cathedral on 28 June 1913.

Supporting paragraphs: George Boscawen, 9th Viscount Falmouth Coldstream Guards
Answer: the Guards Division, Foot Guards regiments