There was “little scientific justification” for border restrictions at the start of the Covid-19 pandemic, as imported cases accounted for fewer than 0.5% of new infections, according to Government documents.

A paper prepared by the Home Office – considered at the end of April by scientists advising the Government – sought advice on a “trigger point” for when to introduce border measures to control cases from abroad.

On June 8, a 14-day quarantine policy was implemented as part of measures to guard against a second wave of coronavirus.

In the paper, discussed by the Scientific Advisory Group for Emergencies (Sage) on April 28, the Home Office said there were ongoing discussions about the possibility of restrictions at the border.

It said that Sage had previously advised imported cases accounted for fewer than 0.5% of Covid-19 cases at the time.

“SAGE previously discussed this issue and concluded that as imported cases account for such a small percentage of total cases (~0.5% at the time), there was little scientific justification for implementing any measures at the border at that point,” the paper said.

But in the paper, the Home Office suggested there will “come a point” when imported infections account for a higher percentage of cases – potentially “mak(ing) a material difference to the UK epidemic”.

The document, prepared on April 27, asked: “Does Sage agree with the principle that if imported cases represent a higher proportion of total UK cases, there would be scientific reason to implement measures at the border?”

Proposed options for measures included screening on arrival, screening prior to travel, a quarantine period and tracking and tracing.

The department asked which of the measures Sage would recommend as being the most effective, and if any other restrictions should be considered.

The paper suggested passengers could be placed in quarantine for 14 days – which would have “large practical implications in terms of accommodation” – or be told to self-isolate upon arrival at their final destination in the UK.

Restrictions could apply to all passengers or just those arriving from higher-risk countries, and could be mandatory or voluntary, the document added.

Under current rules, travellers arriving in the country are required to self-isolate for 14 days or face a fine of up to £1,000 in England.

All passengers – bar a handful of exemptions – must fill out an online locator form giving their contact and travel details, as well as the address of where they will isolate.