Arthur London is headed by the former Joshua founder and managing director Nick Spindler. It won the business from Spindler's former agency after the company approached a number of agencies about the account last month, although no formal pitch was actually held.
The account will include advertising, direct marketing and digital. Joshua, the incumbent on the business, was not asked to defend the account and was given notice by Jacqui Haskins, the M&G marketing director, after three years' work.
Joshua's work on the account included an integrated campaign that ran earlier in the year to commemorate 40 years of the M&G Recovery Fund. M&G's most famous activity was created during the five years it spent working with Harrison Troughton Wunderman.
Among the campaigns created by HTW was a series of cross-track long-copy poster ads that won two silvers at the 2003 Campaign Direct Awards and three golds at the 2002 Direct Marketing Association Awards.
Spindler said: "In its category, M&G has the best creative reputation of any investment house, so to be chosen to take it on to the next stage in terms of its brand ambitions is fantastic and we start with an open brief to see where we can go collectively."
Spindler left Joshua in April 2008 and started Arthur as a consultancy. Its first win was a digital brief for Macmillan Cancer Support, another Joshua G2 client.