Police have released images of a pocket watch worth over £17,000 that was stolen from an antiques dealer in Islington on Saturday.
A man claimed he wanted to buy a vase from the shop in Pierrepont Arcade, off Upper Street, just after midday on December 12.
His payment was declined and as the shop worker returned the vase, it is thought that he opened a display cabinet and stole the 14-carat gold pocket watch.
It was presented to the recipient by former US President Woodrow Wilson, and is thought to be worth between £17,000 and £20,000.
Officers have published a CCTV image of the person they want to speak to.
PC Joshua Brown said: "The owners of this watch are very distressed.
"The item had been in their family for a long time and I would urge the person who stole it to return it as soon as possible."
Anyone with information is asked to call police on 101 quoting CAD 1857/15Dec, or contact the independent charity Crimestoppers anonymously on 0800 555 111.
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