Hindus and Jains across London are celebrating Diwali this Sunday, with Sikhs also marking Bandi Chhor Divas.
In the run-up, shoppers stock up on everything from divas and candles to ghee, rice and Indian sweets.
In the capital's "Little India" in Southall, many supermarkets also now have dedicated Diwali-themed aisles.
But the trend has caused concern among some independent family-run stores who say this commercialisation of Diwali is causing them to lose revenue.
The south Asian community has a strong deep-rooted connection to Southall, in west London, as highlighted in the hit British film Bend it Like Beckham.
The community is now in its second and third generation in the capital and many are seeing their religious festivals being highlighted in mainstream supermarkets.
But some local businesses believe this is at the detriment of their hard work within the community.
'We are the community'
Sira's Cash and Carry in Southall started as a small family business more than 50 years ago in The Broadway and sells south Asian household products.
Indy Sira said: "Diwali is a really special time for us. It's an exciting time where we're celebrating such an amazing occasion.
"It's not that we only understand the community, but that we are the community."
Ms Sira said there was a "noticeable trend" of supermarkets "capitalising" on the festival.
She said the family-run business felt a financial loss when supermarkets began stocking Diwali products.
She wanted to see them acknowledge "the ground work" done by businesses in the community in this area.
She added that businesses such as hers had spent decades building brand awareness of their products which were now being sold in superstores, sometimes at a fraction of the price.
However, some Londoners feel that buying Diwali products in supermarkets has made the festivities more accessible and introduces other communities to the celebration and its associated foods.
Tesco Southall community champion Madhu Rana, who has worked for the company for almost 35 years, said the store's approach has "changed quite a lot in that time".
She said that now there are "huge varieties" of products.
"You can get each and every thing for your Diwali festival," she said.
Store manager Nick Constable said the supermarket also has special aisles for Diwali, Ramadan and Christmas.
"It's a combination of all the diversities of all the religions," he said.
"With the independent businesses, they do their own products and they cook on site as well.
"We do the packaged versions of all of those sort of things, so it gives the customer that choice across all the products."