Current employer causing delay to starting new job

[PensionPuzzle]

I've worked where I am for a couple of months but hated it from day one, and have been fortunate enough to secure a new job which starts imminently.

However due to the nature of the job I can't start until they've had a reference from my current employer, who so far has failed to provide this. It is getting to the point where I will be unable to start my new role on the agreed day (first day after my notice period expires) due to this delay from my current employer.

I've tired politely reminding/chasing the HR person by email but still no joy. Is there anything more that I can do to encourage/compel them to complete the reference so that I don't lose any earnings by having a gap between jobs due to no fault of my own?

Should add the HR does not work on the same site as me so I can't just go and see them in person unfortunately.

Can you phone hr person? Can you give them a deadline or ask them to confirm a timeline?

Can you call HR?

Can your line manager complete a basic reference confirming job role/title, pay grade and sickness via an email?

Can you have a Teams meeting with HR? Spell it out to them. Can you speak with your current manager about this and get their help?

Staff handbook says all reference requests have to be made through and handled by a generic HR@ email address unfortunately, although I think line managers do get asked via this to input. But ultimately it has to go out from HR (safer recruitment process in education which is why it will stop me starting my new job if it's not done in good time).

I've not yet managed to find an internal phone number directory (other than for the first aiders!) but I think I might have to do a bit more digging on that given the silence over the email. Just wish they'd follow their own protocols really!