Tourists were left scratching their heads yesterday after filming for the award-winning TV series Downton Abbey closed a Scots castle.

Visitors were locked out of Inveraray Castle, in Argyll and Bute, while the shooting of the third series of the popular ITV period drama took place inside.

Scotland's tourism agency admitted it was an unfortunate situation for the tourists but said the filming is likely to provide an economic and tourism boost for the Argyll area.

VisitScotland said: "Clearly, it's unfortunate that on this day, tourists have been unable to get into Inveraray Castle. But, hopefully they'll be able to come back again and be welcomed with open arms."

Continuous rain meant the high-profile cast – including Hugh Bonneville and Dame Maggie Smith – were kept inside all day, although Dame Maggie was spotted in full costume.

The 77-year-old actress was seen looking stony-faced and shivering as she made her way into the castle on the banks of Loch Fyne, wrapped in a duffle coat.

Tongues were wagging in the small town as crew members were rumoured to have visited Redshank Designers and Kiltmakers.

They reportedly popped into the shop to arrange for some actors to be fitted out in authentic Scots kilts for an upcoming scene.

Yesterday's shoot is believed to be part of a special Christmas episode.

Writer Julian Fellowes recently admitted he had not yet completed writing the third series, despite filming being under way.

Owned by the Clan Campbell's chief, the Duke of Argyll, Inveraray Castle dates back to the 1400s, although a major fire in 1877 saw the castle take on its current form.