It is the end of an era for Marks & Spencer after the company was relegated from London's FTSE 100 index last night. 

The FTSE 100 contains the 100 biggest UK-listed firms, ranked by market value, and the retailer has been a member since the index was launched in 1984.

The demotion from the prestigious index is symbolic of the company's decline, but it will not affect the day to day running of M&S.

Marks & Spencer escaped relegation on many occasions in the past. At the last relegation, it escaped because it had a well-timed rights issue to fund a delivery venture with Ocado.

Helal Miah, an investment research analyst from The Share Centre in the UK, said M&S is simply lost at the moment.

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"Marks & Spencer has been a stalwart of the UK high street and a benchmark retailer. Whenever we look at the health of the UK retail environment, we generally focus on how Marks & Spencer has been doing," he said. 

"Decades ago it was doing very well, but it's just lost at the moment. It's been left behind by its rivals and it really hasn't caught up with consumer tastes. In terms of its clothing designs, especially its women's wear, it is just not appealing to a younger audience," the analyst said. 

M&S also has its food business which has been doing reasonably well. It did help to support the rest of the business but that growth has been slowing. As Mr Miah puts it; "It can only open so many convenience stores."

"M&S, Tesco and Morrisons are fending off competition from the German discounters. It has become an extremely tough environment, margins are falling and I think it's reflective of what's going on in the UK retail environment as a whole."

The UK high street has also been affected by the shift to online shopping. 

"I think with Marks & Spencer, it hasn't focused on shifting to online. I think it's a classic case where they thought that the high street was always going to be strong.

"Rivals Next are generating more than half of its revenues online. If M&S can't get their online programme together, I don't really see them coming back into the FTSE 100," he added.