NARRATOR: Filming for "Day of the Daleks" began on the 13th of September in 1971.
And it can't be coincidence that the 13th of September is the date given for events in the actual programme.
Can you tell me the exact date?
That's easy.
It was September the 13th.
NARRATOR: The first location was Dropmore Park in Buckinghamshire.
Then owned by the United States International University, the house is a Grade One listed building.
It was built in the 1790s for future Prime Minister William Wyndham Grenville.
Filming here took place over one and a half days, with the first scenes filmed being the ones featuring the guerrilla played by Tim Condren.
In the years after filming, the house was twice badly damaged by fire, and at one point, was in danger of falling into complete ruin.
However, it has been restored to its former glory by a team of property developers.
The rear of the building, here we see a Dalek trying to gain entry, now has a luxurious conservatory attached.
The peaceful atmosphere of this Georgian house gives little indication of the underlying tension.
NARRATOR: The gravel driveway has been tarmacked but otherwise, the property looks as good, if not better, than it did in 1971.
MacINTOSH: Sir Reginald himself has just returned from an 11th-hour meeting in Peking.
(RAY g*n f*ring) NARRATOR: The grounds to the rear of the house were used for the Dalek as*ault.
The gardens are steeped in history and are still recognisable from the 1971 sh**t.
(MACHINE-g*n f*ring) Late in the morning of the second day, after sh**ting all of the material at the front of the house, the production team moved to Brentford, to Harvey House on the Green Dragon Estate.
This collection of high-rise housing blocks was considered distinctive enough to be used as the exterior of the Dalek Headquarters.
The buildings still stand out, and are clearly visible from the M4 as you drive past.
The guerrillas' as*ault on the Dalek HQ in episode four was also filmed here.
However, the underground garages have long been demolished and walled in.
The stairwell is still recognisable.
But the area underneath the block of flats has now been incorporated into the building.
On the 15th and 16th of September, the team moved to an area just north of Bulls Bridge, near Hayes in Middlesex.
The tunnel that features so prominently in the story is still there, but is no longer accessible by foot.
The tow path on the opposite bank is now the only one in use.
And the tunnel can only be accessed if you cross the canal by barge.
The tunnel itself is not very long and had to be carefully sh*t.
Indeed, an amendment to the sh**ting script shows how far short it fell in terms of length.
The bridge is a railway bridge and is still in use.
At the time of filming this Now and Then feature, the bridge was undergoing strengthening work.
The new brickwork is very visible and eats into the archway, so that it no longer has an attractive curve.
This area required multiple permissions for use in 1971, as parts of it were owned by British Waterways, British Rail and the Central Electricity Board.
The waste ground that the Doctor and Unit were seen searching in part one is still waste ground, although very different in appearance.
An elevated section of roadway bisects this area, now separating it from the part which doubled for the 22nd-century wasteland most prominently featured during the trike chase.
The approach to the tunnel from the waste ground, seen so prominently throughout "Day of the Daleks", is now inaccessible from this direction, despite the best efforts of your erstwhile producer.
Not only is this area protected by a huge mound of earth, it is heavily overgrown and cordoned off by a very formidable-looking wire fence.