With effect from 1st January claiming VAT refunds at the airport ceases. The only way to reclaim the VAT will be for the store to post items directly to overseas address. So, customs officers won't be as busy as we think (maybe). This from Gov.UK site:-
"VAT Retail Export Scheme
As part of these changes, VAT refunds for overseas visitors in British shops will be removed. Overseas visitors will still be able to buy items VAT-free in store and have them sent direct to their overseas addresses, while the costly system of claiming VAT refunds on items they take home in their luggage will be ended."
https://www.gov.uk/government/news/duty-free-extended-to-the-eu-from-january-2021