A further definition from The (Alternative) Legal Costs Dictionary:

Specialist costs counsel n. counsel who was once given a brief by his clerk at 7.30pm to appear in Taunton County Court at 10.00am the next morning in relation to the detailed assessment of a bill of costs totalling £3,241.14 but received a text message at 8.30am on the day of the hearing (3 hours into his journey to court) informing him that the matter had been compromised at £2,900.