Spare Desks, Signed Rights: Making Alienation Clauses Work in a UK Office Lease

Most small UK teams enter lease negotiations with a short list: rent, rent-free period, break date and service charge cap. Those are sensible priorities. But a lease can concede all of them and still leave a growing or contracting business with no practical way to use spare capacity. The clause that controls this is usually headed alienation, and it is often skimmed because it sounds like a landlord's concern rather than a tenant's opportunity.

For a twelve-desk team in 2026, the question is rarely whether it will need exactly twelve desks for the whole term. Hybrid patterns, project teams and sideways hires make occupancy uneven. The alienation clause decides whether that unevenness can be managed commercially or whether every adjustment requires a fresh negotiation with the landlord.

Three routes, three different legal effects

Alienation clauses usually refer to three routes, and they are not interchangeable.

Sharing occupation is the lightest option. The tenant remains in occupation and allows another organisation to use part of the premises, often under a licence. A sister company, a partner or a small client team may sit alongside the tenant without a separate lease. The risk is that a badly drafted sharing arrangement can look like a tenancy if the occupier has exclusive possession, pays a market rent and cannot be moved. Labels matter less than substance.

Underletting creates a sublease. The tenant becomes the undertenant's landlord for a defined area or the whole premises, usually for a shorter term than the headlease. The tenant remains liable to the head landlord. The undertenant pays rent to the tenant, not to the head landlord. This is the route most teams mean when they talk about subletting a spare floor or a defined four-desk room.

Assignment transfers the whole lease to a new tenant. It is not a partial solution. Once assigned, the original tenant generally steps out of the landlord-tenant relationship, although older leases and authorised guarantee agreements can preserve liability. Assignment suits an exit, not a temporary sharing arrangement.

Consent is not a formality

Many leases contain a qualified prohibition: dealing is forbidden without the landlord's consent, but consent is not to be unreasonably withheld. In England and Wales, the Landlord and Tenant Act 1988 imposes duties on the landlord to give consent within a reasonable time and not to withhold it unreasonably. That is a useful backstop. It is not a fast track.

In practice, the landlord will want information: the proposed occupier's identity, business, references, intended use, lease terms and plans. Its solicitor will review the underlease or licence. Its surveyor may consider service charge apportionment, insurance and access. A consent that is theoretically available in a few weeks can take two to three months once professional advisers are involved.

The phrase not to be unreasonably withheld also says nothing about the conditions attached to consent. Landlords commonly require a consent fee, reimbursement of legal and surveyor costs, a rent deposit, a guarantee, or alterations to the proposed sublease. Those conditions can be reasonable in principle and still expensive in practice.

Leases in Scotland are governed by a different legal framework, so the statutory language and process should be checked separately. Throughout the UK, the commercial point is the same: the tenant needs to know not only whether consent can be obtained, but how long it will take and what it will cost.

The traps that turn flexibility into a cost

The first trap is professional fees. A landlord may charge a consent fee of several hundred pounds plus VAT, together with its legal and surveying costs. Those costs are often payable whether or not consent is ultimately granted. A tenant should cap them in the heads of terms or, at minimum, require them to be reasonable and evidenced.

The second is the rent deposit. A landlord may ask for a deposit from the undertenant, or from the tenant, as a condition of consent. A three-month deposit is cash tied up for the duration, even if it is returned later. It should be sized to the actual risk, not simply copied from the headlease.

The third is reinstatement. If the undertenant installs partitioning, cabling or a meeting room, the headlease may require the tenant to remove it at the end of the term. The tenant should ensure the underlease passes that obligation down and that any alterations are approved in advance.

The fourth is the mirroring problem. An underlease that conflicts with the headlease on use, access, insurance or service charge can create a dispute between tenant and undertenant that the landlord has no duty to resolve. The underlease should be consistent with the headlease and should be reviewed by a solicitor before consent is sought.

A worked example: twelve desks, four underlet

Consider a twelve-desk suite with headline rent of £54,000 a year, service charge of £9,000 and business rates of £6,000. Total occupancy cost is £69,000 a year, or £5,750 a month. Four desks represent one third of the suite, so the proportional cost is £23,000 a year, or about £1,917 a month.

The team identifies a defined four-desk room that can be underlet for eighteen months at £1,800 a month. Gross income over the term is £32,400. One-off costs are a landlord consent fee of £850, landlord legal fees of £1,250, tenant legal fees of £1,500 and demising works of £2,400, totalling £6,000. If the tenant allows two months for consent and marketing, a further £3,600 of rent is unrecovered.

Net recovery is therefore £22,800 over eighteen months, or £1,267 a month. That is about 66 per cent of the proportional cost of the four desks. The arrangement helps, but it is not a windfall. It also ties up a deposit of £5,400 and creates management obligations for the tenant. The numbers should be tested before the space is marketed, not after the consent application is submitted.

A negotiation checklist for heads of terms

• Define the permitted routes expressly: sharing with group companies, underletting part, underletting the whole and assignment.
• Require landlord consent not to be unreasonably withheld or delayed, with a stated response period for complete applications.
• Cap consent fees and legal costs, and make them payable only where reasonably incurred.
• Limit any rent deposit to the actual risk and require its return within a fixed period.
• Confirm that any underlease must mirror the headlease and that the landlord will not unreasonably object to a standard form.
• Address reinstatement before alterations are made, not at the end of the term.
• Check how service charge, insurance and utilities will be apportioned for a partial underletting.
• Confirm access, signage and permitted use for the proposed occupier.

Alienation clauses rarely win a negotiation on their own. They are, however, the difference between a lease that can breathe with the business and one that locks a small team into its first-floor plan. The time to test that flexibility is before signature, when the landlord still has an incentive to agree.