Question: The Sir Ralph Abercromby is the only structure remaining in St Peter's Field after cavalry charged into a crowd had gathered to demand the reform of what? 

Context paragraphs:
Peterloo Massacre: The Peterloo Massacre occurred at St Peter's Field, Manchester, England, on 16 August 1819, when cavalry charged into a crowd of 60,000–80,000 who had gathered to demand the reform of parliamentary representation.

George Abercromby, 2nd Baron Abercromby: George Abercromby, 2nd Baron Abercromby (14 October 1770 – 15 February 1843) was a Scottish lawyer, politician and peer.  The eldest son of Lt.-Gen.  Sir Ralph Abercromby and Mary Abercromby, 1st Baroness Abercromby, he became, like his grandfather, a lawyer, and was called to the Bar in 1794.  On his death in 1843 he was succeeded in the barony by his son.

Invasion of Trinidad (1797): On February 18, 1797, a fleet of 18 warships under the command of Sir Ralph Abercromby invaded and took the Island of Trinidad.  Within a few days the last Spanish Governor, Don José María Chacón surrendered the island to Abercromby.

Robert Abercromby of Airthrey: General Sir Robert Abercromby {'1': ", '2': ", '3': ", '4': "} (21 October 17403 November 1827), the youngest brother of Sir Ralph Abercromby, was a general in the army, a knight of the Bath, and at one period the Governor of Bombay and Commander-in-Chief of the Bombay Army and then Commander-in-Chief, India.

Sir Ralph Abercromby (pub): The Sir Ralph Abercromby, also known as the Abercrombie, is a pub in Manchester.  It is named after Ralph Abercromby.  It is located on Jackson's Row, Bootle Street.  Originally built in the 19th century, it is the only structure remaining in St Peter's Field from the time of the Peterloo Massacre.  Wounded people from the massacre were brought to the pub for medical treatment.  Many later changes were made to the building, both inside and outside, with no substantial 19th century features remaining.  It is thought to be the inspiration for the local pub in "Life on Mars".

Rafael Conti: Rafael Conti Flores, also spelled "Conty" (1746–1814) was a Colonel in the Spanish Army who was in charge of the Puerto Rican Militia in the town of Aguadilla.  In 1790, he captured 11 enemy ships involved in smuggling stolen goods.  In 1797, he helped defeat Sir Ralph Abercromby and defend Puerto Rico from a British invasion in Aguadilla.  In 1809, he organized a military expedition fight with the aim of returning Hispaniola, which now comprises the nations of the Dominican Republic and Haiti, back to Spanish rule.

John Colborne, 1st Baron Seaton: Field Marshal John Colborne, 1st Baron Seaton (16 February 1778 – 17 April 1863) was a British Army officer and Colonial Governor.  After taking part as a junior officer in the Anglo-Russian invasion of Holland, Sir Ralph Abercromby's expedition to Egypt and then the War of the Third Coalition, he served as military secretary to Sir John Moore at the Battle of Corunna.  He then commanded the 2nd Battalion of the 66th Regiment of Foot and, later, the 52nd Regiment of Foot at many of the battles of the Peninsular War.  At the Battle of Waterloo, Colborne on his own initiative brought the 52nd Regiment of Foot forward, took up a flanking position in relation to the French Imperial Guard and then, after firing repeated volleys into their flank, charged at the Guard so driving them back in disorder.

Baron Abercromby: Baron Abercromby, of Aboukir and of Tullibody in the County of Clackmannan, was a title in the Peerage of the United Kingdom.  It was created on 28 May 1801 for Mary, Lady Abercromby, in honour of her late husband, the noted military commander Lieutenant-General Sir Ralph Abercromby, who died from wounds received in the Battle of Aboukir in 1801.  The latter was the grandson of Alexander Abercromby, Member of The Scottish Parliament for Clackmannanshire from 1703 to 1707, younger son of Sir Alexander Abercromby, 1st Baronet, of Birkenbog (see Abercromby baronets).  Lady Abercromby was succeeded by her eldest son George, the second Baron.  He represented Edinburgh and Clackmannan in the House of Commons.  On his death the title passed to his son George, the third Baron.  He sat as Member of Parliament for Clackmannanshire, Stirling and Clackmannan and Kinross.  He was succeeded by his eldest son, the fourth Baron.  He was Deputy Lieutenant of Stirlingshire in 1860.  He was childless and was succeeded by his younger brother John, the fifth Baron.  He was President of the Society of Antiquaries of Scotland.  On his death in 1924 without male issue the barony became extinct.

Abercromby Square: Abercromby Square is a square in the University of Liverpool, England.  It is bordered by Oxford Street to the north and Cambridge Street to the south.  It is named after General Sir Ralph Abercromby, commander of the British Army in Egypt, who was killed at the Battle of Alexandria in 1801.

Baron Dunfermline: Baron Dunfermline, of Dunfermline in the County of Fife, was a title in the Peerage of the United Kingdom.  It was created in 1839 for the Whig politician and former Speaker of the House of Commons, the Honourable James Abercromby.  He was the third son of Sir Ralph Abercromby and Mary Anne Abercromby, 1st Baroness Abercromby (see Baron Abercromby for earlier history of the family).  The title became extinct on the death of his son, the second Baron, in 1868.

Supporting paragraphs: Sir Ralph Abercromby (pub) Peterloo Massacre
Answer: parliamentary representation