While opponents of the coalition will be marching through central London, a group of political historians will gather not far from Westminster to attend a seminar on the Liberal experience of coalition governments.
Lloyd George was in coalition with the Conservatives
Interest in coalitions has been revived following Nick Clegg's decision to take his party into government with David Cameron's Conservatives.
But in the first half of the 20th century, coalitions of one sort or another were a common occurrence.
But the experience of the Liberals in coalition was often unhappy.
Carolyn talked to two contributors to the seminar, Professor Vernon Bogdanor, author of 'The coalition and the constitution', and Alun Wyburn-Powell, biographer of the former Liberal leader, Clement Davies.
Vernon Bogdanor argues that coalitions have been bad for Liberals because they cause splits.