Question: The leader that requested the Marble Arch in Libya to be built was the "heir apparent" of what dictator?

Context paragraphs:
Marble Arch Caves Global Geopark: The Marble Arch Caves Global Geopark straddles the border between Northern Ireland and the Republic of Ireland.  It is centred on the Marble Arch Caves and in 2001 it became one of the first Geoparks to be designated in Europe.

Duke of Rothesay: Duke of Rothesay (Scottish Gaelic: "Diùc Baile Bhòid" , Scots: "Duik o Rothesay" ) is a dynastic title of the heir apparent to the British throne, currently Prince Charles.  It was a title of the heir apparent to the throne of the Kingdom of Scotland before 1707, of the Kingdom of Great Britain from 1707 to 1801, and now of the United Kingdom of Great Britain and Northern Ireland.  It is the title mandated for use by the heir apparent when in Scotland, in preference to the titles "Duke of Cornwall" (which also belongs to the eldest living son of the monarch, when and only when he is also heir apparent, by right) and "Prince of Wales" (traditionally granted to the heir apparent), which are used in the rest of the United Kingdom and overseas.  The Duke of Rothesay also holds other Scottish titles, including those of Earl of Carrick, Baron of Renfrew, Lord of the Isles and Prince and Great Steward of Scotland.  The title is named after Rothesay on the Isle of Bute, Argyll and Bute, but is not associated with any legal entity or landed property, unlike the Duchy of Cornwall.

Western Marble Arch Synagogue: The Western Marble Arch Synagogue (WMA) was founded in 1761.  Currently located in Great Cumberland Place, Westminster, in greater London, the Western Marble Arch Synagogue is a leading Orthodox Judaism place of worship.  The result of a merger between the Western and the Marble Arch Synagogues, the synagogue offers religious and social activities to its members and the wider community.

Marble Arch Caves: The Marble Arch Caves are a series of natural limestone caves located near the village of Florencecourt in County Fermanagh, Northern Ireland.  The caves are named after the nearby Marble Arch, a natural limestone arch at the upstream end of Cladagh Glen under which the Cladagh River flows.

The Montcalm Hotel: The Montcalm hotels are a group of luxury hotels in central London, England.  The group includes The Montcalm London Marble Arch and The Marble Arch by The Montcalm London, both of which are near Marble Arch, as well as M By Montcalm Shoreditch London Tech City, located in Shoreditch.  The Montcalm at The Brewery London City and London City Suites by Montcalm, both of which are located in the City of London, round out the hotel chain.  Each of the sites is a five-star hotel .  The Montcalm London Marble Arch was acquired by Shaftesbury Hotels in 2008.

Marble Arch (Libya): The Marble Arch, also Arch of the Philaeni (Italian: "Arco dei Fileni" ), formerly known in Libya as El Gaus (i.e. "The Arch"), was a monument in Libya built during the days of Italian colonization.  The arch marked the border between Tripolitania and Cyrenaica, and was located on the actual Libyan Coastal Highway (at that time "Via Balbia") near Ra's Lanuf.  It was designed by architect Florestano Di Fausto in response to a request by the Italian Governor-General Italo Balbo.  It was unveiled on 16 March 1937 in a lavish night ceremony attended by Benito Mussolini.

Italo Balbo: Italo Balbo (Ferrara, 6 June 1896 – Tobruk, 28 June 1940) was an Italian Blackshirt ("Camicie Nere", or CCNN) leader who served as Italy's Marshal of the Air Force ("Maresciallo dell'Aria"), Governor-General of Libya, Commander-in-Chief of Italian North Africa ("Africa Settentrionale Italiana", or ASI), and the "heir apparent" to Italian dictator Benito Mussolini.

Church of the Annunciation, Marble Arch: The Church of the Annunciation, Marble Arch, is a Church of England parish church in the Marble Arch district of London, England.  It is dedicated to the Annunciation to the Blessed Virgin Mary.  It is a Gothic revival building designed by Sir Walter Tapper and built in 1912–1913.  It is a Grade II* listed building.

Connaught Place, London: Connaught Place is an area in the Bayswater area of the City of Westminster (a London Borough).  The nearest underground station to Connaught Place is Marble Arch tube station which is a few minutes to the East near Marble Arch walking past the site of the Tyburn Tree.

Odeon Marble Arch: The Odeon Marble Arch (known as the Regal 1928-1945) was a cinema located opposite Marble Arch monument at the top of Park Lane, with its main entrance on Edgware Road, London.  It operated in various forms from 1928 to 2016, and is most famous for once housing a vast screen capable of screening films in 70mm.

Supporting paragraphs: Marble Arch (Libya) Italo Balbo
Answer: Benito Mussolini