I've had 10-15 transits go walkies in the london / essex area all stolen the same way with NO damage to exterior or igntion locks.
they lower dash trim is always removed and the OBD port exposed.

5 have turned up in the same trading est after having the sliding doors cut open (extra slam locks fiited to the back of the van) and the safes emptied.

i have been in discussion with ford and supplied them with a ignition barrel with summit snapped off in it as they got disturbed and legged it.