Submitted by EdelmanAgency IPI Score 94/100

Mayo Hack (Mayo McHack)

Influencer Marketing

Hellmann's used McDonald's own ordering system to serve mayo with fries at a chain that refused to stock it, driving an 842% rise in social impressions.

320%Engagement increase
9ptPurchase intent increase
46%Brand consideration boost
842%Social impressions increase

About the campaign

Hellmann's, the UK's number one mayonnaise brand, had no route to one of the country's biggest fries audiences: McDonald's UK did not offer mayo as a dip, and a spokesperson had publicly declared there was not enough demand for it. Edelman London turned that quote into both brief and antagonist, spotting the gap between what the chain refused and what it already sold: the Mayo Chicken burger contained mayo, so anyone who de-selected the chicken, lettuce and bun on the ordering screen was left with just the condiment.

The Mayo Hack turned every McDonald's order screen in the UK into a route to mayo with fries, no permission required. Edelman promoted the workaround through DOOH screens placed outside McDonald's restaurants, regional print ads and Hellmann's own social channels, while five foodie influencers published instruction videos and the team reached out directly to hundreds of people who had previously asked McDonald's on social media for mayo, a pre-qualified audience of the frustrated. Customers who posted a photo of their hack were reimbursed the burger's 1.19 pound cost by Hellmann's.

Edelman reports an 842 percent increase in social impressions, a 320 percent rise in engagement, a 46 percent boost in brand consideration and a 9-point lift in purchase intent, and the campaign won at The One Show 2024 in the Direct Marketing, Non-traditional and Guerrilla category.

Case in 60 seconds

Hellmann's, the UK's number one mayonnaise brand, could not get its product to one of the country's biggest fries audiences: McDonald's UK did not offer mayo as a dip and a spokesperson publicly stated 'there's not enough demand for it.'

McDonald's already sold a menu item containing mayo — the Mayo Chicken burger — meaning its own ordering system could theoretically deliver mayo to any customer who knew how to customise the order. Edelman identified this gap between what the chain refused and what it already offered.

The Mayo Hack instructed customers to de-select the chicken, lettuce and bun from a Mayo Chicken order on the McDonald's ordering screen, leaving just the mayo — turning every McDonald's order screen in the UK into a route to mayo with fries.

Edelman promoted the hack via DOOH screens outside McDonald's restaurants, regional print ads, and Hellmann's own social channels. Five foodie influencers made instruction videos, and the team reached out directly to hundreds of people who had previously asked McDonald's on social media to add mayo. Customers who posted a photo of their hack were reimbursed the £1.19 cost of the burger by Hellmann's.

Edelman reports a 842% increase in social impressions, a 320% rise in engagement, a 46% boost in brand consideration, and a 9-point increase in purchase intent. The campaign won at The One Show 2024 in the Direct Marketing, Non-traditional & Guerrilla Marketing category. All effectiveness figures are agency self-reported.

Strategy Breakdown

The primary strategy-learning section — interpretation, not a press-release summary.

Hellmann's targeted McDonald's UK customers who wanted mayo with their fries, including a specific sub-group of people who had already publicly asked McDonald's on social media to add mayo as a dip — a pre-qualified audience with demonstrated intent.
Mayonnaise is described as the most popular condiment in the UK, yet the country's largest fries seller declined to offer it, using a public 'not enough demand' rationale. That statement created a visible contradiction between consumer preference and what was available at the point of purchase.
A condiment brand cannot easily place its product on the menu of a fast food chain that has chosen not to stock it. Hellmann's had no route to the McDonald's fries occasion through conventional distribution or partnership.
Hellmann's acted as the enabler of a workaround, giving customers the knowledge and a small financial incentive to obtain mayo where it was otherwise unavailable. The brand did not ask McDonald's for permission; it used what McDonald's already sold.
People who had already complained publicly about the absence of mayo at McDonald's were a ready-made activation group. Reaching out to them directly with a solution converted existing frustration into campaign participation without requiring the brand to build demand from scratch.

Creative & Execution System

Assets & channels

  • DOOH screens placed outside McDonald's UK restaurants
  • Print ads in regional UK newspapers
  • Hellmann's owned social channels
  • Five foodie influencer instruction videos
  • Direct social outreach to prior McDonald's mayo requesters

Partners

  • Edelman / London (lead agency, per The One Show 2024 attribution)

Participation mechanic

  • Customise a McDonald's Mayo Chicken burger order to remove chicken, lettuce and bun, leaving only mayo
  • Post a photo of the completed hack
  • Receive £1.19 reimbursement from Hellmann's equal to the burger cost

Creator role

  • Five foodie influencers produced and published instruction videos demonstrating the hack to drive social engagement and normalise the behaviour

Results & Evidence

MetricValueResult typeConfidence
Social impressions842% increaseReachAgency reported
Social engagement320% riseEngagementAgency reported
Brand consideration46% boostBrand metricAgency reported
Purchase intent+9 percentage pointsBrand metricAgency reported
Respondents wanting Hellmann's at McDonald's72% of respondentsSurvey / sentimentAgency reported

Awards & Recognition

Award showYearCategoryResultSource
The One Show2024Direct Marketing, Non-traditional & Guerrilla MarketingWinner—

Why Edelman's strategy worked

  1. 1

    Building an activation on an existing menu item meant no partnership or permission from McDonald's was required. The hack worked entirely within McDonald's own ordering infrastructure, removing the biggest structural barrier to the campaign.

  2. 2

    Anchoring the campaign to a public, quotable refusal — the McDonald's spokesperson's 'not enough demand for it' statement — gave the work a clear premise and a concrete story to tell, rather than a generic brand message.

  3. 3

    Direct outreach to people who had already publicly asked McDonald's to add mayo converted pre-existing, documented demand into first participants, reducing the cold-start problem for an earned social campaign.

  4. 4

    A small, simple reimbursement (£1.19 per hack posted) created a low-cost incentive structure for user-generated content without requiring a complex prize mechanic or significant media budget.

  5. 5

    Layering influencer instruction videos over the owned and DOOH activity gave new audiences a low-friction way to understand and replicate the hack, extending organic reach beyond Hellmann's existing followers.

  6. 6

    The multi-channel distribution — DOOH near McDonald's locations, regional print, owned social, influencer, and direct outreach — matched the message to contexts where the target behaviour (ordering at McDonald's) was most likely to occur or be recalled.

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