City analysts aren’t generally known for their fashion flair but last night they were given first sight of key pieces in the crucial autumn-winter ranges that Marks & Spencer hopes will woo Britain’s middle-class, middle-aged shoppers back through its doors once again.

The attendance of M&S chief executive Marc Bolland at the swanky event, held in an imposing neoclassical church in London's Marylebone, underlines just how important the collection is for Britain's biggest clothing retailer. Its sales have been falling for the past two years and Bolland is pinning his hopes for a revival on these ranges, the first full collection his new fashion team has put together.

Bolland’s hopes of keeping his job may also depend on just how well the ranges are received. It is exactly three years since the Dutch-born former Heineken boss took over as chief executive from Sir Stuart Rose and clothing sales at Britain’s best-known retailer have remained on the slide.

Revolving door
The revolving door at M&S's head office has been in frequent use since Bolland moved into the hot seat, with a stream of exits and arrivals of senior executives and creative types.

Key appointments include the elevation of M&S insider John Dixon, who headed up the successful food side of the group, to oversee the core general merchandise division, which takes in clothing, and Belinda Earl, former Debenhams and Jaeger boss, as style director. Both executives were in attendance alongside their chief executive last night.

The departures have included Kate Bostock, who was once seen as a potential successor to Rose but who departed a year ago amid talk of a clash with Bolland and frustration at the slow pace of change. Another key appointee, Janie Schaffer, known as the "Knicker Queen", quit in April after just three months at the group.

The City has been patient so far but, with the new team largely assembled, shareholders want to start seeing results.

M&S has been attempting in recent days to play down the importance of the autumn- winter collection, billed by many fashion experts as “make or break” for the group – and its chief executive.

In the run-up to the catwalk show, it has also been outlining its strategy in less glamorous but equally important areas, such as distribution.

Last week, analysts visited M&S’s new 900,000sq ft warehouse in Castle Donington, which will handle online orders and store deliveries. It is part of the group’s £1 billion (€1.18 billion) programme to update its creaky infrastructure and enable its outdated delivery network to cope with the demands of multichannel retailing. At peak times, the fully automated warehouse in the midlands will handle up to a million orders a day.

But, like improvements to the fashion ranges, speeding up the distribution system is taking longer than expected. The programme started before Bolland arrived, in 2009, and still has some way to go.

Bolland has also been stepping up M&S’s international expansion, something all but abandoned by management more than a decade ago. When he took over in 2010 Bolland set out a plan to double international sales by 2014, with a target of £1 billion.

Some investors fear M&S may be making the same mistake as Tesco – spending too much time on its international ambitions at the expense of the core UK operation. At the heart of the UK operation is womenswear, where M&S has been losing customers to more fashionable rivals such as Zara, H&M, Debenhams and Next.

Recent figures showed the group’s share of the clothing and footwear market had fallen to 11.1 per cent from 11.5 per cent a year ago.

Reputation for quality
In an effort to address this, M&S is cutting back on its muddle of sub-brands, streamlining its ranges and attempting to reassert its reputation for quality to keep its middle- aged customers happy without alienating younger, more fashionable shoppers. It is also tidying up its store layouts, which customers have complained are hard to navigate.

After last night’s presentation for analysts and the business press, fashion writers get their turn with a full catwalk show today. The fashionistas will be swift, and no doubt brutal, with their verdicts. But it’s the M&S shopper who’ll have the final say when the new ranges appear in the stores from July.

Fiona Walsh writes for the Guardian in London