The year is 1963: the border to East Germany is closed and the Iron Curtain has descended with a merciless thud. Berlin is a divided city, its western and eastern zones eying one another with unflinching suspicion. Any attempt to leave East Berlin now means risking life and limb. Escape artists devise one new method after another – digging tunnels, scrambling improvised aircraft and, of course, modifying all manner of vehicles to whisk away the new band of refugees. But nobody had thought of using a BMW Isetta; how, after all, could you hide anyone within its miniscule frame? Klaus-Günter Jacobi found a way, handing his childhood friend a passport to the freedom for which he yearned. This adventure at the meeting point between the two Germanys would write its own chapter in history.

Klaus-Günter Jacobi was living in West Berlin when a childhood friend approached him with a plea. Manfred Koster implored Jacobi to help him flee East Germany, by now completely sealed off from the West. Time was of the essence, as Koster had been drafted to the army and couldn’t afford to hang around.

Escaping the clutches of the Iron Curtain called for extraordinary cunning. An order to shoot was in force at the border fences and guards carried out meticulous checks at the crossings. Cars were subject to particularly rigorous searches. Klaus-Günter Jacobi needed an idea nobody had thought of before. Enter the Isetta – all 2.30 m (length) and 1.40 m (width) of it – which Jacobi had been the proud owner of for some time. The notion of using the jaunty “bubble car” as an escape vehicle seemed absurd, but maybe this would also make it perfect for the job at hand.

As a trained car mechanic, Klaus-Günter Jacobi knew exactly what needed to be done – and that the work would take a long time. Cue a purpose-made metal canister to replace the fuel tank, a raised parcel shelf below the rear window, modifications to the exhaust pipe and shift linkage, and a flap to crawl into the space from the interior. To complicate matters further, the car’s inspection certificate was about to expire and it would be impossible to secure a new one with all the changes. He was actually stopped by police during a test drive, but fortunately that was in West Germany and the plan was still on.

As a West Berliner, Klaus-Günter Jacobi wasn’t allowed to enter East Germany, so he couldn’t drive the escape vehicle himself. And a medical student from Stuttgart who initially volunteered lost her nerve at the intimidating sight of the border with all its sentries, dogs and glaring spotlights. Would all of Jacobi’s efforts ultimately be in vain? Then came a phone call from a guy calling himself Werner, who had heard talk of the plan and was willing to put his – and his friend’s – neck on the line. On 23 May 1963, Jacobi and Werner set off, with the latter’s friend following in a VW Beetle.

A new special exhibition running at the BMW Museum until 8 March 2020 details the daring escape aboard the Isetta. Visitors who back themselves to get out again can inch inside a box roughly the size of the space in the escape car – and in so doing relive an episode in modern history. Not that the Museum box’s occupants will have to endure the chilling suspense of a border check while they’re inside.