Both the mansio and the bath-house at Letocetvm stand on a westward-facing slope which overlooks the shallow valley of a tributary of the Crane Brook. The ground surface is terraced so that floors in the mansio are about 8 ft. 6 in. above the entrance steps of the baths. Traces of cultivated allotment gardens were recorded by aerial photography to the north-west of the mansio.
The mansio was an official imperial posting hostel built to provide lodging for messengers, couriers and other imperial officials travelling along Icknield Way and Watling Street.
The site was originally occupied by a courtyard building of cream-plastered wattle-and-daub and roofed with thatch, with at least a part being decorated with a brown and red linear pattern. It was adjoined on its north-east corner by some sort of military storage building or granary. Construction methods suggest that these buildings were contemporary with the barrack blocks of the Neronian fortress, i.e. circa 54-64 AD. They were demolished by fire, probably by accident, in the early Flavian period.
The next building to occupy the site had deep foundation trenches with posts supporting plastered walls, again of wattle-and-daub construction, but this time decorated by rectangular embossed patterns and multi-coloured floral designs. Built in a courtyard plan in the Flavian period, this building contained at least 8 rooms on its northern side laid out in a long range and possessed glass windows.
Associated with this building but separate from it in a large, open courtyard was a large, well, 8 ft. by 6.5 ft. and over 25 ft. deep. The regularity of its construction suggest that it was built by military engineers, though why a well should be built when there was a perfectly adequate water supply from the nearby brook remains a mystery. It has been suggested that the well was some sort of shrine to a local water-deity, as several curiously-carved stones, possibly from the well-head were found buried face-down in the vicinity. The scarcity of votive items found in the well causes problems for this theory, but they may well have been cleared out by the Romans prior to starting the phase-3 buildings, which were erected directly over it.
The Flavian building remained in use until around 140-150 AD when it was demolished to allow construction of the mansio. This atrium style building was by far the most sophisticated on the site, having massive stone foundations and being at least two stories high.
Facing Watling Street, the mansio was approached by a paved path laid on gravel, and fronted by a colonnade with a tiled roof, probably supported on wooden columns. The eastern end of the colonnade seemed to have been utilised as a workshop area for the repair of carriages and the like, and a door here led to a large room in the south-east corner of the main building, perhaps an interior workshop.
In the centre of the colonnade, opposite the gravel approach path, a large door formed the main entrance to the interior of the building. Through this door was a narrow vestibule area where guards possibly checked the credentials of anyone seeking admittance. A narrow door in the centre of a wooden partition led to the entrance hall beyond.
Through the entrance hall was a colonnaded atrium or courtyard with a plastered floor, the central area probably being open to the sky and perhaps containing a herbaceous garden. A semicircular area at the near end had much lighter foundations than the rest of the building, and was probably the base for a statue or other decorative feature. Timber posts resting on these foundations around the edges of the colonnade supported a balcony above.
The entrance hall was flanked on either side by similarly sized rooms probably accessible from the central courtyard. The one on the west contained washing facilities and a gutter leading to a soakaway in the central part of the building, the function of the room to the east remains unknown, though it may have been a guardroom.
On the western side of the courtyard were three small rooms which opened out onto the central colonnade at ground level. The function of these rooms is uncertain, but they were probably used as private accomodation for users of the mansio. A narrow room in the south-west corner of the building next to the washroom was accessible from the southernmost of these three rooms, which was slightly longer than the other two. This room probably contained stairs leading up to the second storey and also down to the level of the cobbled road between the mansio and the adjacent bath-house, where a small door gave access to the street.
A narrow room leading off the courtyard in the north-western corner may have contained another set of stairs leading up to the balcony above. This stairwell was bordered on the east by two other guest accomodation chambers, which were also accessible from the central colonnade.
The largest room in the mansio lay in the north-east corner, and was of such dimensions that the colonnaded walkway was reduced in width in this area. The chamber was heated by a channelled hypocaust system added some time after the building was first completed. A passageway beside this room led from the central colonnade to the outside via a door in the east side of the structure.
Two more rooms lay on the east side of the central courtyard, the one nearest to the hypocaust chamber was most likely the mansio kitchen. This theory is supported by the fact that a domestic rubbish dump was situated against the eastern wall near the side exit, and is backed up by its proximity to the heated room. A narrow shelf was built into the wall to the south at its western end, the exact function of which remains unknown. The remaining room on the east side was probably another one used to accommodate guests, but again, this cannot be confirmed.
It is thought, though it cannot be confirmed, that the three square rooms on the western side of the mansio and the stairwell in the north-west corner had the area beneath them available for storage, and that these storage spaces were accessed from outside at street level. These storage rooms could therefore have formed a row of four small tabernae making the area between the mansio and bath-house into a street-market.
To the north of the mansio, adjoined to it but inaccessible from within was a collection of buildings built a few years prior to the mansio itself. These were probably used as stables and tack storage rooms.
Most, if not all, of the rooms on the ground floor were adorned with decorative wall friezes and had glass windows. To sum up, this was a building of distinction, constructed by military engineers and used for some official imperial purpose.