Scatters of Roman material have been found in Fleet Marston since the 1950s and it was always thought that it denoted the presence of a fort along the line of Akeman Street (the modern A41). Aerial photographs taken of a field south-west of St Mary’s church show the vague outline of a building that may also be of a Roman date. Fieldwalking in the 1970s north-west of Putlowes recovered early Roman pottery, roof tiles and noted some possible robbed out walls in the section of a modern field ditch, adding evidence to this theory. In 1990 some houses were built in an area north of Putlowes and a later Roman pottery and some flue tile from the walls of a Roman building were found. Metal-detecting in this area has also recovered Roman coins, a key, buckles, animal bone and pottery including amphora sherds. One metal-detectorist found some lead and copper smelting waste, suggesting some industry in this area and discovered that in the 1980s the farmer had found the lead lining of a Roman coffin in this area, which was later donated to Buckinghamshire County Museum. The farmer had also uncovered a possible Roman hypocaust (the underfloor heating system) nearby in the 1960s. A spectacular find of a pewter hoard was made by the same metal-detectorist in 1995.
A smaller scatter of Roman pottery was also found west of Fleet Marston Farm. More was found during archaeological investigation of a pipeline in 1998. Pits, ditches and a road excavated east of Lower Blackgrove Farm were dated to the Roman period. The evidence of Roman activity at Putlowes was reinterpreted as a small town extending along the A41 at the point where it forded the River Thame. A further extension of this town was also found next door in Billingsfield in Quarrendon parish.
Fleet Marston is recorded in Domesday and was on the edge of Bernwood Forest from before that time. Bernwood had been a hunting forest from the time of Edward the Confessor. It grew to its largest extent under Henry II. The whole area was not covered by woods; in the medieval period a forest was a place where deer roamed for hunting and so included open land, villages and fields. All those who lived in the forest were not allowed to hunt or even gather wood without a special licence from the king. Bernwood Forest was finally disafforested in the reign of James I in 1635, although it had been shrinking in size since the time of King John (1199-1216).
St Mary’s church is the oldest surviving building in Fleet Marston parish. Due to the lack of parishioners it was declared redundant in the 1970s. Excavations before restoration at this time uncovered at least 17 medieval burials in the nave of the church. The remains of the deserted medieval village lie to the north-west of the church but have been much disturbed by roadworks and ploughing. 13th and 14th century pottery has been found on the ground surface here. The medieval manor house, which was taken down in 1772, is recorded as having stood near the church and there is a large house platform immediately west of the church that may be the site of it. There may have also been another settlement at Putlowes in the medieval period, but there is not much evidence of it.
Some buildings may have survived until quite recently. Two house platforms south-west of Lower Farm may be post-medieval farm buildings and geophysical survey noted one had a hearth in the centre. A historical map of the area in 1694 marks the field north of the church as Millers Mead and as this is bounded on the north by a stream, it is possible that this was the site of a watermill in the medieval or post-medieval period. There is a mound north-west of Putlowes that may be a prehistoric barrow but is more likely to be a medieval or post-medieval windmill mound. Not many buildings survive in Fleet Marston parish. Fleet Marston Farm is listed and dates back to the 17th century in parts.