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I grew up in Wiltshire all too aware of the Ministry of Defence's major presence in the county, especially on Salisbury Plain.

We all knew that there were top secret establishments, including one where spooks and boffins researched mysterious and deadly weapons of germ warfare. That was Porton Down.

But the thought of getting anywhere near, let alone inside, never crossed anyone's mind.

Porton Down has long since been split into two establishments; one Ministry of Defence, the other civilian.

The latter is now on the front line of the effort to detect and minimise the risk of Ebola appearing in the UK. I was given rare and exclusive access to the site, run by Public Health England.

Known as PHE Porton, the centre carries out research on infectious diseases, and works with the private sector and universities on new products such as vaccines.

Crucially, given international concern about Ebola, Porton has a key role in response to potential emergencies.

This is where tests on suspected Ebola cases are carried out. Diagnostic services are provided for clinicians across the UK.

Porton Down has known all about Ebola since it was identified in 1976.

A closely guarded sample of the virus was brought to the UK to be examined and to allow further research.

But a potentially fatal mistake was made by a Porton scientist who accidentally came into contact with the virus in a laboratory.

He developed severe fever symptoms but survived after being treated in isolation at the Royal Free Hospital in North London (which has the facilities to treat any patients developing Ebola from the current outbreak).

That Ebola sample has remained at Porton ever since - in tightly controlled conditions.

It is part of a deadly collection which includes anthrax and plague. They are stored at temperatures as low as minus 80C (176F).

I was assured that the freezer units which contained these killer samples were behind several secure doors, each requiring access codes.

The corridors of Porton seem anonymous and little changed since the 1950s.

Only the occasional sign saying "novel and dangerous pathogens" and "emergency showers" betrayed the nature of the work being carried out. There is a brisk and businesslike atmosphere with no sense of panic or crisis.

The message from Porton is that Ebola is just one of a number of threats which are being monitored.

Officials have long been used to dealing with several samples every week, particularly at this time of year with many long-distance travellers arriving in the UK.

Doctors contact the Imported Fever Service run by Public Health England with details of cases needing further examination. Samples are then dispatched to Porton.

Lassa fever, yellow fever and dengue are high on the list of diseases which Porton is looking out for.

A testing process lasting about seven hours will look for traces of these and other viruses as well as Ebola.

There has been a threefold increase in the number of cases referred to Porton since Ebola gained a national media profile as clinicians take an ultra cautious approach.

So far no Ebola case has been identified in the UK.

Dr Tim Brooks, who heads up Porton's work on rare and imported pathogens, told me that he and his colleagues were not unduly concerned about Ebola because dealing with dangerous diseases was part of day-to-day life.

He said they were well practised in testing routines and how to handle positive cases.

In July this year the Porton team dealt with a case of the infectious and potentially deadly Crimean-Congo haemorrhagic fever.

A British traveller was said to have responded well to treatment. A patient who arrived in the UK with the fever in 2012 subsequently died.

Here on the site surrounded by woodland in the Wiltshire countryside, nobody is taking anything for granted.

But there is a sense that they are ready for anything and that they are well prepared should Ebola arrive in the UK.