Its existence is known from only one entry in the Antonine Itinerary, a listing of routes and facilities for the cursus publicus, the official courier service of the Roman Empire.

Sulloniacis, which is recorded in Iter II (Itinerary II) for the route that ran between Portus Ritupis (Richborough, Kent) and Deva Victrix (Chester, Cheshire), was nine Roman miles from Verulamium (St Albans) and 12 from Londinium (London).

Roman remains found at Brockley Hill near Edgware in the London Borough of Barnet have been identified as those of Sulloniacis.

Aside from the evidence of pottery production and some domestic buildings, modern excavations have failed to find any remains of mutationes (stations for changing horses) or mansiones (accommodation for official travellers).

[4] A 4.2 ha (10 acres) Site of Borough Importance for Nature Conservation, Grade II, located immediately south-east of the Brockley Hill archaeological site at Grid Ref TQ176940 has been named Sulloniacis Pastures.