The United Kingdom stands out from the other countries in the study due to its electoral system. Unlike other European countries, the UK  has a pure majoritarian electoral system. This system strongly favours the emergence of a two-party system and has been of great significance for the absence of anti-establishment parties in the country. Even parties that gather a relatively large share of the votes usually receive very few seats in parliament. For example, the Liberal Democrats, long the third-largest party in the country, received just over eleven percent in the 2019 election but only got one percent of the seats in the House of Commons.

Another consequence of this is that radical views have often been accommodated within the major parties. Labour has thus housed militant, radically socialist factions, while the Tories have accommodated national conservative factions.