What is the correct way of including break clause in lease?

The scenario is as follows

•Lease start date: 01/01/2020

•Lease end date : 31/12/2060

•Break clause expected to be exercised: 31/06/2040 [Agreement between lessor and lessee to end lease or to continue the same based on the internal business decision]

•Rent of £10k per annum at start but increases £3k every 10 years

•Paid monthly in arrears

•Discount rate of 10% in FY39 but reduced to 8% in FY40

Thanks.

Atul