Shares in Marks and Spencer jumped on Friday afternoon on rumours that private equity titan CVC Capital Partners is considering a takeover offer for the High Street group.It is thought that CVC is looking at an bid and has approached executives both inside and outside the firm "about a possible management role under private equity control," according to Bloomberg which has spoken to unnamed sources close the matter.Shares in M&S fell the day before as analysts at Santander said that the company would be too expensive for private equity funds or sovereign wealth funds given its £8.2bn enterprise value. "While we agree that M&S has a strong brand heritage, we do not believe that there would be an appetite at current levels," a Santander analyst was quoted as saying.At today's prices, M&S's market capitalisation is around £5.9bn.The firm reported last month that like-for-like sales slipped by 0.7% in the 13 weeks to June 30th as falling general merchandise revenues offset strength in the food division.Shares have dropped steadily since hitting a 52-week high of 389.5p in March, but have picked up in recent weeks on the back of takeover speculation.Before the close today, the stock was trading at 367.6p, up 3.11% on the day.