Security of tenure is the tenant's right to have the lease renewed when the landlord wishes to terminate it. A tenant achieves the right to security of tenure after a rental period of two years according to the Rental law. The security of tenure one has as a sublease tenant is relatively weak and the sublease tenant would need to move out should the primarily tenant request to move back into the tenancy.
If the rental period are to continue longer than for two years and the primarily tenant would like the sublease tenant to agree to waive their right to security of tenure, a separate agreement approved by the Rent Tribunal could be needed. When a tenant waives their right to security of tenure, agreements that lasts for up to four years normally gets approved when they have acceptable reasons listed in the application sent to the Rent Tribunal.