Can't find Vehicle Interface Connector in battery box

[squowse]

I want to connect up a 3rd AGM battery for leisure use (campervan). Following the BEMM instructions to connect to switched ground "engine run" to close an isolating relay.
Got seat off, both batteries out and still cannot find this connector! I thought it was meant to be on every transit. This is a UK 2012 mk7 rear wheel drive with the dual AGM battteries. 2nd hand and the previous users had auxiliary electronics but off the starter battery as far as I can tell. Their equipment was mostly removed.
Please see pics