John Lewis’ new project with Alice Temperley is the latest in a long line of partnerships between retailers and designers – with M&S teaming up with Terence Conran and H&M signing up a collection of big names, the trend shows no sign of going away.

Alice Temperley will create a line called Somerset for the retailer, which will be her first collection for the High Street in an ongoing partnership with the company.

John Lewis’ tie up reinforces comments made by its chairman Charlie Mayfield at the Cloud Retail Week’s conference in March, when he spoke of the importance of products that can’t be bought elsewhere.

He said at the time: “It has never been more important to develop and source products which are what your customers really want and can only buy from you.”

The tactic is increasingly popular with retailers keen to stand out from the crowd. “It has become a much larger trend because it helps retailers stand out, and celebrities and designers have an influence on how we spend,” says Verdict analyst Maureen Hinton.

Debenhams has partnered with a string of designers including Julian MacDonald, while Specsavers hired Gok Wan to design a range of exclusive spectacles.

But there’s always the possibility of overkill – if everyone does it, the effect of designer partnerships could start to be watered down. “You’ve got to be careful or it dilutes the impact,” says Hinton.

What will matter is the product. If the designer in question does manage to create things people want to buy – as with H&M’s more successful initiatives such as its Marni project – a retailer could be on to a winner. If the products aren’t exciting, a big name can only create so much hype by itself.

It’s also important to be selective. It’s easy to throw money at a celebrity or designer who doesn’t fit with a retailer’s brand – the effect will be a confused marketing image, and potentially flagging sales. Jamie Oliver and Sainsbury’s were a good match, for instance, because of a specific focus on quality food.

Celebrities with erratic behaviour – such as footballers – should be avoided, Hinton advises.

And as with any marketing plan, it’s important to be flexible. H&M does well because it moves quickly and is capable of tapping into the talent of different designers at different times.

The biggest impact on sales will be felt when there’s excitement and interest around a collaboration, and as boredom sets in, longer term partnerships will need refreshing or replacing.