The proposed 'temporary' move of a special needs school has led archaeologists to discover evidence of Romano British farming activity on the playing field site of the former Howe Dell School near the town centre. The HLHS reports:

Hatfield has a recorded history going back to the Norman Domesday book of 1086 when 55 families were noted as living here at ‘Hetfelle’. And there was certainly a human presence over a century before during the Saxon period when, in 970, King Edgar gave Hatfield to the monks of Ely. But before then, things become a bit sketchy for local evidence of the  earlier Romano-British period.
Hatfield is bordered by the Roman town of Verulamium in St. Albans to the west, and the famous Welwyn Baths - part of a substantial Roman villa - a bit to the north. Roman track- ways are known to pass through Panshanger and Colney Heath. And Devils Dyke in Wheathampstead was a stronghold of the Catuvellauni tribe where Julius Caesar is said to have paid a surprise visit around 54 BC. A hoard of Roman coins was found in Essendon a few years ago. A Belgic settlement was discovered at Letty Green  and an ancient farmstead unearthed at Stanborough.
The question begs itself : If  there, why not here?
But Hatfield only has a marble bath to show for its possible Roman era connection.
Until now.
In September, archaeologists conducted a thorough survey of the old Howe Dell School playing field sited between Woods Avenue and Rectory Drive. They scraped at least 2 feet
of top soil from an area of about an acre and discovered clear evidence of farming activity.
Archaeologist Wesley Keir writes:
“The predominant features found in the excavations were thirteen parallel, shallow linear trenches which are likely to represent Late Iron Age/Roman cultivation trenches. Similar features identified on sites elsewhere are thought to have been used to grow soft fruits such as grapes [and olives]........In the eastern end of the excavation area was a  larger probable boundary ditch of an apparently earlier rectangular enclosure upon which the cultivation trenches were superimposed. A rubbish pit containing Roman pottery, brick and roof tile was located to the north-west of the enclosure...”
As the cultivation plot investigated was only confined to an
available section of the former Howe Dell playing field - due to
it being surrounded by housing and roads - it was therefore
probably part of a larger area. And where there is farming of any
substantial scale, there is usually a farm house.
Perhaps the “Roman pottery, brick and roof tile..” found on the
site are artefacts from a Roman styled villa located nearby.
Whatever the merits of this suggestion, the site was evidently
farmed at least 2000 years ago, and for some considerable time too,
thus adding further credibility to the likelihood of local habitation. 
          The final report is expected in the new year.