Investec has departed the RBS Shareholders Action group, represented by Signature, to join Mishcon’s group just weeks after the firm entered the High Court battle by attracting the Lloyds Bank institutional investors on their £420m claim for damages.

Mishcon partner Richard Leedham is leading representation for the asset management group and two of its funds.

The firm is also understood to be in talks to apply to the High Court to become a lead claimant group in the action. Such a move would increase the financial exposure of the Mishcon group, but could reap rewards pending a successful outcome on the case.

The Mishcon group is privately funded whereas Signature has a third-party litigation funder putting up a pot for the claimants.

Following the Lloyds investors’ jump to Mishcon a number of sources close to the litigation said that other firms, including Fladgate and an unnamed US player, were understood be approaching Signature’s claimants to launch further splinter groups.

Fladgate previously represented the RBS Shareholders Action Group but came off the record following a disagreement over funds.

The departures from the Signature action group signal a splintering between the retail and institutional investors bringing claims against RBS.

It is also understood the departures represent a change in direction on the institutional investors’ legal battle, moving away from Signature’s targeting of individuals in the action, namely RBS’s former chief executive Fred Goodwin and three other directors.

The claimants across all five groups allege the bank’s £12bn rights issue in 2008 was defective and contained “material misstatements and omissions”.

As well as Investec, Mishcon’s group includes claimants such as Scottish Widows, Clerical Medical Investment Group, Halifax Life and HBoS Investment Fund managers.

Individual investors of Investec remain in the Signature group.

The Lloyds move prompted speculation the splinter group could be bowing to pressure from senior banking officials to end its claim against RBS entirely. A source said it was “embarrassing” for Lloyds’ institutional investors to be suing another publicly-funded UK bank.

Signature came on the record for the principal claimant group this summer following a disagreement over funds with its previous counsel Fladgate. The swap marked the second in this case, with the group previously turning to Bird & Bird.

Stewarts Law, Leon Kaye and Quinn Emanuel Urquhart & Sullivan represent the other claimant groups. The case is scheduled for December 2016.

RBS is represented by Herbert Smith FreehillsThe Lawyer revealed in September the firm’s bill up to the end of a trial on quantum would hit £90m.

A spokesperson for the RBS Shareholders Action group said: “Investec’s decision makes no difference to the RBoS Shareholder Action Group. It has no claim against RBS. Its clients do. They continue to be members of our group, and they have told us they do not wish to change this situation.”

Mishcon declined to comment other than to confirm it was now on the record for Investec.

Investec and Signature Litigation declined to comment.

The legal line up

For claimants, the Royal Bank of Scotland Shareholders Action group

3 Verulam Buildings’ Jonathan Nash QC, Peter de Vernueil Smith and Ian Higgins, instructed by Signature Litigation partner Graham Huntley

For claimants, the Stewarts Law group

3 Verulam Buildings’ Andrew Onslow QC, Adam Kramer and Scott Ralston, instructed by Stewarts Law partners Clive Zietman, Keith Thomas and Fiona Gillett

For the claimants, the Leon Kaye group

3 Verulam Buildings’ Michael Lazarus, instructed by Leon Kaye partner Leon Kaye

For the claimants, the Quinn Emanuel Urquhart & Sullivan group

One Essex Court’s Laurence Rabinowitz QC, Erskine Chambers’ Alex Barden and One Essex Court’s Maximillian Schlote, instructed by Quinn Emanuel partners Sue Prevezer QC and Martin Davies.

For the claimants, the Mishcon de Reya group

Mishcon partner Richard Leedham. Counsel is not yet known.

For the defendants, RBS 

Fountain Court’s David Railton QC and James McClelland, Serle Court’s David Blayney QC and Simon Hattan, 3 Verulam Buildings’ Sonia Tolaney QC, instructed by Herbert Smith Freehills partners Simon Clarke, Adam Johnson and Kirsten Massey. 7KBW’s Jonathan Gaisman QC, previously lead counsel, has come off the case