The pair of raiders dressed in high-visibility jackets to swipe the JCB from roadworks on the M25.
They then drove it into a nearby Tesco Express store, stealing cash and the safe during the daring raid early this morning.
A Metropolitan Police spokesman said the raid caused “substantial damage”.
The suspects loaded the store safe on to a white lorry before escaping.
Both suspects are described as male, about 6ft tall and wore balaclavas.
The Met spokesman said: “Officers are appealing for any witnesses to the incident to come forward and assist them with the investigation.
“They are also appealing for anyone who may have seen people stealing the JCB digger from roadworks near the junction with the A127 to come forward.”