The relationship between an expert witness and the instructing solicitor is a contractual one, whether or not it has been reduced to writing. So if your fee and the timing of its payment have been agreed, the solicitor is contractually responsible for paying that fee in full and within that time span.

You will hear some or all of the following excuses from lawyers:

• I’ve not yet been paid by the client, so I cannot pay you;
• I didn’t receive the full amount, so I cannot pay you the full amount; and
• I can only pay you what was allowed after assessment of the costs.

All the above have absolutely no bearing on the contract you have with the solicitor, who must pay you in full and on time. Any contract variation should have been agreed in advance.