Heading northbound past the Gas Works and new School on an iron ore train, the headcode is 8N61, David J Hayes has an official London Midland Region (LMR) BR booklet for train identification codes, which I believe dates from the 1960s when four-character displays were introduced. As well as internal letter codes for trains operating within the LMR, there are the usual inter-regional codes - e.g. E (Eastern), M (London Midland), O (Southern), S (Scottish) and V (Western) - and also the latter N, which indeed stood for North Eastern. Hence, this picture could well be an iron-ore working from Kettering/Wellingborough to somewhere like Cargo Fleet or South Bank as mentioned in his comments on D38.