Still on a Peter Gill jag, I came across this page (on the website I discovered earlier this week) about the production of Kick for Touch at the National in 1983.
I saw it. In those days I caught a lot of productions on the South Bank as I used to commute on the train from Waterloo and would often pop in of an evening if I had nothing better to do then catch the train home after the show.
The picture of Jane Lapotaire and the kids on the right brought back some memories. As I recall she appears with them at the very last moment of the very last scene. Memory may play tricks but I can't remember the boy and girl appearing in the rest of the production at all.
On the way home, I recognised them (escorted by their Mum) as we all boarded the same train. When their mother spied an acquaintance, the friend, I and the rest of the carraige were subjected to a long lecture on her offspring's histrionic brilliance.
For all I know they may be giants of contemporary theatre by now, but twenty odd years ago it did seem like hilarious over-egging of the pudding to hear them praised to the skies for a five second, non-speaking, walk-on part.