Hunter is hiding giant versions of its top clip backpacks around London.
The inflatable backpacks will be in the capital for three days from 11 October before appearing in Boston, US and Tokyo, Japan.
For the scavenger hunt, people can retrieve clues from Hunter's social media channels and look out for the backpacks, which stand at between seven and 10 metres. Anyone who finds one can scan the QR code for a chance to bag themselves a £5,000 reward.
Hunter’s focus on backpacks is part of its continued efforts to reaffirm itself as a multi-category brand.
Alasdhair Willis, creative director at Hunter, said: "Hunter’s bag sales continue to grow significantly across all our markets, with bags in our Japanese market now accounting for 45% of sales. We wanted to leverage this momentum and continue to drive awareness and engagement with our bags offer in Hunter’s key markets – the UK, US and Japan.
"The 'Hunt the backpack' campaign is a way to digitally engage both our existing customer and a new audience, amplified by social. Landing a series of giant backpacks, in key central London locations, delivers to a wider audience a new perspective and access to the Hunter brand."
The larger-than-life activation follows other big activities for the brand, including a 120ft Hunter "flying boot" hot air balloon that has been on a global tour since 2018.
The project is being delivered in-house.