UPDATE 1-M&S names Robert Swannell chairman

* Swannell joins board on Oct. 4 as non-exec director

* To become chairman Jan. 4

* Stuart Rose to leave company on Jan. 4

* Shares up 2 pct

(Adds detail, background)

LONDON, Aug 23 (Reuters) - Marks & Spencer (MKS.L), Britain's biggest clothing retailer, has added some investment banking clout to its boardroom, naming veteran City heavyweight Robert Swannell as Stuart Rose's successor as chairman.

Confirming media speculation, M&S said on Monday that Swannell would join the board on Oct. 4 as a non-executive director and become non-executive chairman on Jan. 4. [ID:nLDE67J0Z1]

Swannell, 59, is a former chairman of Citi's (C.N) European investment bank and vice chairman of Citi Europe and the current chairman of music, books and games retailer HMV Group (HMV.L).

Rose will stay as chairman until the latter date when he will leave the retailer, some three months earlier than his previously stated last possible departure date of the end of March.

"It is a privilege to be asked to chair one of the world's greatest brands," Swannell, who is also a non-executive director of British Land (BLND.L) and 3i Group (III.L), said in a statement.

The appointment completes the restructuring of M&S' board.

Marc Bolland, the former boss of Wm Morrison Supermarkets (MRW.L), succeeded Rose as chief executive in May, while Alan Stewart was appointed finance director earlier this month.

The appointment will also see M&S revert to standard governance practice.

Rose has had a rocky relationship with institutional shareholders since he combined the roles of chairman and CEO in 2008 against corporate governance guidelines.

Rose will depart M&S after six and a half years at the firm. He was initially parachuted into the retailer in 2004 to fend off a takeover approach from billionaire retail entrepreneur Philip Green, a defence that Swannell, then at Citi, advised on.

Shares in M&S were up 1.9 percent at 339.2 pence at 1142 GMT, valuing the business at 5.4 billion pounds ($8.4 billion). (Reporting by James Davey; Editing by Mark Potter)