If the UK leaves the EU without a deal, you’ll need to declare cash or bankers drafts of £10,000+

UK Govt notice issued today (3.6.19)

“If the UK leaves the EU without a deal, you’ll need to declare cash of £10,000 or more (or the equivalent in another currency) up to 72 hours before arriving in the UK.Cash includes:

• notes and coins
• bankers’ drafts
• cheques of any kind (including travellers’ cheques)”

Travelling in the EU

“If you bring cash to the UK from another EU country, you do not need to declare it. You may need to declare cash you take to other EU countries - check with the authorities in the country you’re travelling to.”