Harborough Magna services would have been on the M6 between J1 and J2, exactly half way between Corley and Watford Gap. The site has four 'ghost slips' which used to have full road markings, but these were removed presumably because drivers were mistaking it for an exit.
To incorporate the landscaping and picnic areas motorists were starting to expect, the site identified at Harborough Magna was huge: originally 16 acres. It would have come into use when the neighbouring alternatives were full.
In 1979 there were doubts that the services would be built and the land was turned back into agricultural land, but on the basis that the Department for Transport would take over if they thought another service area would be required. Technically this agreement still applies, but the Department are no longer responsible for identifying potential services.
The two fields were originally connected by a footbridge which had no steps up to it, leaving it hanging in the air. This was removed in around 2004. Both of the fields connect to Old Montilo Lane, the road which was used before it was dissected by the M6 and Montilo Lane moved onto a new alignment. On both sides the road has gated access onto the east-facing 'ghost slips', although the one on the westbound side doesn't look all that official.
Harborough Magna replaced a previous plan for services at Stretton-under-Fosse, which would have required considerable earthworks to bring it into use.
Today, Extra want to build a service area close to this site, although the exact location isn't clear.