Question: Which county in England is home to British former Liberal Democrat Member of the European Parliament, Diana Wallis?

full_context: Document 1: Diana Wallis: Diana Paulette Wallis, {'1': ", '2': ", '3': ", '4': "} (born 28 June 1954 in Hitchin, Hertfordshire) is a British former Liberal Democrat Member of the European Parliament (MEP) for Yorkshire and the Humber. Wallis was first elected in 1999 and re-elected in 2004 and in 2009. She resigned her seat in January 2012. On 26 April 2013, she became an Honorary Fellow at the Law School of the University of Hull (UK).
Document 2: Hatfield, Hertfordshire: Hatfield is a town and civil parish in Hertfordshire, England, in the borough of Welwyn Hatfield. It had a population of 29,616 in 2001, increasing to 39,201 at the 2011 Census. The settlement is of Saxon origin. Hatfield House, the home of the Marquess of Salisbury, is the nucleus of the old town. From the 1930s when de Havilland opened a factory until the 1990s when British Aerospace closed, Hatfield was associated with aircraft design and manufacture, which employed more people than any other industry.
Document 3: Marina Yannakoudakis: Marina Yannakoudakis (born 16 April 1956) is a member of the European Economic and Social Committee and a former Conservative Member of the European Parliament for London. She was elected at the 2009 European Parliament election. She lost her seat at the 2014 election.
Document 4: Middlesex: Middlesex ( , abbreviation: Middx) is a historic county in south-east England. It is now entirely within the wider urbanised area of London. Its area is now also mostly within the ceremonial county of Greater London, with small sections in other neighbouring ceremonial counties. It was established in the Anglo-Saxon system from the territory of the Middle Saxons, and existed as an official unit until 1965. The historic county includes land stretching north of the River Thames from 3 mi east to 17 mi west of the City of London with the rivers Colne and Lea and a ridge of hills as the other boundaries. The largely low-lying county, dominated by clay in its north and alluvium on gravel in its south, was the second smallest county by area in 1831.
Document 5: Fiona Hall (politician): Fiona Jane Hall MBE (born 15 July 1955 in Swinton, Lancashire), née Cutts, was a Member of the European Parliament for North East England and leader of the Liberal Democrat MEPs., until the 2014 European Election. She was elected to the European Parliament in 2004, and re-elected in 2009, coming in third behind Labour and Conservative candidates with 17% of the vote, the highest of any UK Liberal Democrat candidate.
Document 6: East of England: The East of England is one of nine official regions of England at the first level of NUTS for statistical purposes. It was created in 1994 and was adopted for statistics from 1999. It includes the ceremonial counties of Bedfordshire, Cambridgeshire, Essex, Hertfordshire, Norfolk and Suffolk. Essex has the highest population in the region.
Document 7: Hertfordshire: Hertfordshire ( ; often abbreviated Herts) is a county in southern England, bordered by Bedfordshire to the north, Cambridgeshire to the north-east, Essex to the east, Buckinghamshire to the west and Greater London to the south. For government statistical purposes, it is placed in the East of England region.
Document 8: Meral Hussein-Ece, Baroness Hussein-Ece: Meral Hussein Ece, Baroness Hussein-Ece, (born 10 October 1953) is a British Liberal Democrat member of the House of Lords. She is the first woman of Turkish Cypriot origin to be a member of either house of Parliament after she was appointed a Liberal Democrat working peer on 28 May 2010. She has been the Liberal Democrat Spokesperson for Equalities since 2015.
Document 9: South Oxhey: South Oxhey is a suburb of Watford in the Watford Rural parish of the Three Rivers district of Hertfordshire, England. It is located in the south western corner of Hertfordshire and close to the boundary with Greater London. At the 2011 Census South Oxhey's population was included in the Northwick Ward of Three Rivers Council.
Document 10: Leavesden, Hertfordshire: Leavesden is a residential and commercial area in Hertfordshire, England, contiguous with the northern suburbs of Watford. It lies within the M25 Motorway. On its eastern side it is bounded by the M1 Motorway. Leavesden is part of Abbots Langley civil parish and is also the name of a district council ward in Three Rivers District. Leavesden Green is an adjoining residential community which lies partly in Three Rivers and partly in the Borough of Watford.
Document 11: Jolanta Dičkutė: Jolanta Dičkutė (born December 8, 1970 in Kaunas) is a Lithuanian politician and Member of the European Parliament for the Labour Party; part of the Alliance of Liberals and Democrats for Europe. She was studying at the Kaunas Medical University from 1989 to 2002 to earn PhD in public health.
Document 12: Essex: Essex is a county in the East of England immediately north-east of London and is one of the home counties. It borders the counties of Suffolk and Cambridgeshire to the north, Hertfordshire to the west, Kent across the estuary of the River Thames to the south and London to the south-west. The county town is Chelmsford, which is the only city in the county.
Document 13: Hertford Loop Line: The Hertford Line (also known colloquially as the Hertford Loop) is a branch of the East Coast Main Line, part of the Northern City Line commuter route to London for Hertford and other Hertfordshire towns and an occasional diversion route for the main line. The line is part of the Network Rail Strategic Route 8, SRS 08.03 and is classified as a London and South East Commuter line.
Document 14: Jenny Willott: Jennifer Nancy Willott (born 29 May 1974) is a British politician. She was the Liberal Democrat Member of Parliament for Cardiff Central from 2005 to 2015. Willott became a junior minister in the Department for Business, Innovation and Skills and Government Equalities Office in December 2013, temporarily standing in for Jo Swinson while she was on maternity leave. She is the first woman and first Liberal Democrat to represent her seat. She was a councillor in the London Borough of Merton from 1998 to 2000.
Document 15: Wallis Simpson: Wallis, Duchess of Windsor (born Bessie Wallis Warfield; also known by her married names of Wallis Spencer and Wallis Simpson; 19 June 1896 – 24 April 1986) was an American socialite whose intended marriage to King Edward VIII caused him to abdicate his throne.
ground_truth: Hertfordshire