The construction of the M4 flyover, or Motorway On Stilts courtesy of British Pathe from 1963.
Footage from April 1963, courtesy of Huntley Film Archives, showing the Great West Road including (briefly)the Lucozade factory by large M4 roadworks, Brentford area, past light industry, Martini clock tower, the Wimpey building and Gunnersbury Park.
The opening of the M4 flyover in 1964, again courtesy British Pathe.
The History of Brentford 
I remember when the M4 was being built local people had no idea what was going up. I recall my parents speculating with our neighbours in the street just what it might be.
I remember going on the homes before roads March.I was only a small child and had to wear a gas mask.
I left school in 1963 and my first job was with Marples Ridgeway, Keir, Christiani and Nielson, the engineering firms building the flyover. I was the telephonist and I answered “Marples Ridgeway, Keir Christiani and Nielson all day! At 16 I was terrified at the Christmas party and escaped climbing out of the toilet window pushing the Christmas turkey gift through the small temporary office window and running home with the turkey, (with feathers and gizzards).
Theresa Hooper
hahaha… fantastic account š