Local health chiefs believe Christmas Day was the tipping point that forced Boris Johnson to put the country into another lockdown.
The Prime Minister last night told the country to 'Stay at Home' and only go out for essential reasons or face a fine, with kids learning from home until mid-February at least.
Northamptonshire's Director of Public Health pointed to a sharp spike in positive tests on December 29 as the "tipping point" which left the Government with no alternative.
The number of new cases in Northamptonshire jumped by around a fifth on that day — a rise which was mirrored across the country — and by a further 15 per cent the following day.
Restrictions were eased slightly on December 25 allowing some families and friends to get together for Christmas.
Lucy Wightman said: "If people contract the virus they start to develop symptoms somewhere between three and five days after exposure.
"So, if you think about Christmas Day being the likeliest point when people mixed because of looser restrictions, then they are likely to develop symptoms around the 29th."
Last night's announcement came as a shock to some but Mrs Wightman insisted it is necessary to help ease pressure on local NHS services.
Numbers of coronavirus-positive patients being treated at Northampton and Kettering hospitals jumped between Christmas and New Year with 272 occupying beds.
Mrs Wightman added: "The NHS is coping but staff are having to ascertain day-by-day what they can and can't provide from point of view of business as usual operations. Some outpatient services and elective surgeries have had to be stood down.
"A rise of nearly 30 per cent in the number of Covid positive patients has a significant impact on the number of beds available for non-Covid patients.
"There is also pressure on staff because they have to self-isolate if they contract Covid.
"The national lockdown is the right thing to do, although I was surprised the Government didn't opt to go for a 'Tier Five' to keep economies open in areas with lower rates.
"We've seen and been victim to situations where people have travelled in to Northamptonshire from other areas because we had lower restrictions for a period of time.
"I'm glad that science has prevailed in this case, but I thought there might be more pressure politically."
Official figures are published five days in arrears to allow for corrections but raw data from Public Health England revealed Northamptonshire saw more positive Covid tests in one day than in a whole week just eight weeks ago.
Tuesday's provisional figure of 731 new positive swabs in 24 hours was higher than the 624 during seven days to October 5.
Northampton also saw its highest daily number of positive tests 310. The borough now has a weekly rate of over 700 positives per 100,000 people compared just over 500 a week ago.
Three other areas of the county — Corby, Daventry and South Northants — also have rates in excess of 500.