https://www.slab.org.uk/guidance/expert-witnesses-costs/
https://www.slab.org.uk/guidance/expert-witnesses-costs/
Unusually large expenditure is defined as expenditure on a single item of work above £2,000 (excluding VAT), where the proposed expenditure has not already been covered by a grant of approval in relation to experts or unusual work.
Where the cost of instructing an expert to provide a report would cost more than £2,000, this would require approval for an expert witness, not unusually large expenditure.
If we have already provided approval for an expert witness to provide a report, and you need to cite the expert to give evidence in court, where this is expected to cost more than £2,000 (and again, where this involves a single rather than cumulative cost above the threshold), a request for approval for unusually large expenditure will also be required. The original grant under expert prior approval does not cover this work where the expected cost of a single item (e.g. travel) is more than £2,000.
Otherwise, where the cost of work is below the unusually large threshold set out above, our prior approval is not required before the work is undertaken.
However, if the work is unusual in nature, our prior approval is always required, regardless of proposed cost.