---
title: Third-Party Harassment Is Where the New Duty Gets Difficult
description: From 30 October, UK employers must prevent harassment by clients and contractors too. What two tribunal rulings show about getting investigations right.
---

[A blog about being human at work | Human by Practice](https://humanbypractice.co.uk/blog)

# [Third-Party Harassment Is Where the New Duty Gets Difficult](https://humanbypractice.co.uk/blog/third-party-harassment-is-where-the-new-duty-gets-hard)

 Written by [Jess Sandham](https://humanbypractice.co.uk/blog/author/jess-sandham) | Oct 8, 2026, 10:19:07 AM

## A duty that doesn't stop at your own staff

From 30 October, UK employers face a strengthened duty to take all reasonable steps to prevent sexual harassment at work. The duty already covers harassment between colleagues. It also covers harassment by clients, customers, contractors and anyone else an employee deals with while doing their job. Most harassment-prevention training assumes the person causing harm reports to someone inside the business. That assumption breaks down the moment the harasser is a customer at the till, a contractor on site, or a client on a video call.

*Photo by [Vitaly Gariev](https://unsplash.com/@silverkblack?utm_source=human_by_practice&utm_medium=referral) on [Unsplash](https://unsplash.com/?utm_source=human_by_practice&utm_medium=referral)*

## Why third-party harassment is harder to investigate

A grievance about a colleague follows a process HR already runs: interview the complainant, interview the accused, review the records, reach a decision. A complaint about a client or contractor has none of that structure. The evidence sits with a third party who has no obligation to hand it over. There is no disciplinary process to run against someone who doesn't work for the business. And there is rarely a clear escalation route written into the contract behind the relationship.

Employers who rely on training alone are solving the wrong problem. Training tells staff what harassment looks like and how to report it. It gives the business no contractual leverage over a client who harasses staff, and no escalation route when a contractor's own employer won't act. Both have to exist before training can do its job.

*Photo by [Clay Banks](https://unsplash.com/@claybanks?utm_source=human_by_practice&utm_medium=referral) on [Unsplash](https://unsplash.com/?utm_source=human_by_practice&utm_medium=referral)*

## What two tribunals show about investigation standards

Two recent rulings show how closely tribunals now examine the quality of an investigation, separate from the behaviour it covers.

In Mateo v British Airways, the tribunal accepted that a steward's "mile-high club" comments and unwanted touching towards a colleague actually happened and were blameworthy. It still found his dismissal unfair. BA interviewed him before it had taken a full account from the complainant, and the tribunal called the investigation rushed and one-sided. His award was cut by 50% for contribution and Polkey combined, but the dismissal itself stood as unfair.

In Hayes v Secretary of State for Justice, a prison officer was fairly dismissed for repeated unwanted touching and sexual advances towards male colleagues, after clear earlier warnings that the behaviour was unacceptable. The tribunal found the dismissal proportionate because the warnings were documented and the escalation was consistent.

The two cases make the same point from opposite directions. Believing a complaint is not enough on its own. A complete investigation, taken in the right order, is what protects an employer at tribunal, whatever the outcome turns out to be.

*Photo by [Dimitri Karastelev](https://unsplash.com/@dkfra19?utm_source=human_by_practice&utm_medium=referral) on [Unsplash](https://unsplash.com/?utm_source=human_by_practice&utm_medium=referral)*

## What to do before 30 October

Three steps matter most in the time left before the duty tightens.

First, map where staff face clients, customers, contractors or the public without a manager present, and treat those points as risk. Retail counters, home visits, helplines and site work all qualify.

Second, build an escalation route for third-party harassment into contracts and supplier agreements. A clause that lets a business remove a contractor or end a client relationship matters more than a policy filed in a handbook nobody outside the business reads.

Third, audit how investigations actually run against what the policy claims happens. Sequence matters: complainant first, full account taken, then the accused. Mateo and Hayes both turned on sequence and documentation, not on whether the underlying behaviour was serious enough.

HBP's harassment-prevention training covers all three areas: recognising third-party risk, building the contractual and policy infrastructure behind it, and running an investigation that holds up at tribunal. The law changes on 30 October. The gap it exposes, in most organisations, is already there.

[View full post](https://humanbypractice.co.uk/blog/third-party-harassment-is-where-the-new-duty-gets-hard)

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