I have the following information, which may be of interest to Beathead and Andrew Martin. All the episodes exist at the BFI.
There is an explanation as to why. I'm surprised the BBC haven't made copies of the other episodes as it must be about the only complete BBC television children's serialized drama from the 1950s. A 'must have' with respect to the BBC television archive I should have thought.
The Silver Sword" (BBC TV - 1957)
The cast:
Brenda Dunrich .... Mrs. Wolff
Melvyn Hayes .... Edek Balicki
Frazer Hines .... Jan
Barry Letts .... Joseph Balicki
Pat Pleasence .... Ruth Balicki
Ingrid Sylvester .... Bronia Balicki
Gwen Watford .... Magrit Balicki
George Woodbridge .... Mr. Wolff
Michael Balfour .... American G.I. (appearance at the conclusion of last episode.)
Screenplay by C.E. Webber
Based on the novel by Ian Serraillier
Runtime: 30 min (7 episodes)
The episodes for The Silver Sword are as follows:
The Escape from the Nazis, broadcast date 24.11.57
Escape from Prison, broadcast date 01.12.57
The Burning of the City, broadcast date 08.12.57
The Return of Edek, broadcast date 15.12.57
Jan in Trouble, broadcast date 22.12.57
Escape from Bavaria, broadcast date 29.12.57
The Last Lap, broadcast date 05.01.58
When the National Film Archive appointed the first Television Acquisitions Officer in 1959, this was the first serialized television drama made for children to be chosen, and the earliest in this category to be donated by the BBC.
Yours,
ANDy