Is it essential?
Yes — you should always check that any contractors you hire for your event have their own insurance. Here's why this is important, and what to check:
The insurance provided by Event Insurance does not extend to cover contractors you hire (for example, for security, catering, staging, lighting, sound, etc.).
If a contractor causes injury or property damage during setup or during the event, any claim would likely be their responsibility — and only their own insurance can respond.
As a minimum, you should ask contractors for evidence of a valid Public Liability insurance policy. If they have staff (employees or sub-contractors), they may also need Employers' Liability insurance.
Checking their insurance helps protect you as the event organiser — it ensures that third-party claims do not fall back on you just because you're coordinating the event.