So how tall was Valentino and is it possible now to find out? Well I sent out a couple of inquiries. The first was to Anda Rowland, the gov'nor of his London tailors Anderson & Sheppard; Anda Rowland immediately replied and promised to look into their records and did so the next day. The second was to Campbell's funeral parlour in New York. They laid Valentino to rest, and have not yet replied. When they do, I'll put up the result.
The Anderson & Sheppard ledgers show that Valentino was measured by them on 21st November 1925 and, from the following measurements (note the contemporary comment on the shoulders), the current head cutters in that firm estimate that Valentino was 'approximately six feet tall':
Very sloping shoulders
Overcoat length 62"
Jacket length 31"
Outside leg 42"
Inside leg 32"
High waisted rise 10"
This all comes from one of the best firms of tailors in the world and it goes without saying that one accepts the figures; after all they made perfectly fitting clothes from them. Moreover, they certainly well-disguised the sloping shoulders, just as Hawes & Curtis did for Robert Donat, who suffered from the same condition.
It seems generally to be accepted that Greta Garbo was five feet seven tall. Here is a picture of her with John Barrymore in a film still: