Back in the very late 1950s, DP lived in Malaysia. It was the time when transistor radios had just appeared on the market.
In Asia, they were a fraction of the price in the UK and DP bought both my sister and I radios , and as they were both (usually) scrupulously honest, they gave us the invoices and cash to pay customs duties on our way back into the UK.
DS and I decided to play the innocents, we showed the customs officer the radios, but when they asked how much they cost, we looked wide eyed with shock and said that they were presents and we didn't know, so they went away, came back and valued them at £5.00 each, which was half of what they actually cost, so we paid the duty and pocketed the change.
Now whether that counts as smuggling or just clever footwork I am not sure