SOLVED. 1950/60s Children's book re time travel via a maze/cave/labyrinth [s]

[JAW]

I'm trying to track down a UK (?) children's book I read in the 1960s.
The book involves two boys or young men finding a maze or labyrinth from which various exits allow them to explore the past. I seem to recall them meeting a caveman within and following him to explore his time and world. At the end they encounter someone from their future who bars their way. The book title may include the term 'maze' or 'labyrinth'.
The book was a hardback and available in late 1960s England.
I can’t find ‘hide nor hair’ of this excellent novel on the web and would love to read it one more time. Any help to that end would be enormously appreciated.

[Tab]

The Time Maze by Reginald Maddock seems to fit.

Five Boys in a Cave fits a little.

Do you remember the time period the story takes place? Where was the labyrinth located? Behind a castle, in a park, a mythical country, etc?

Anything about the cover?

[JAW]

Dear Tab - you've solved it! A conundrum that's been troubling my early hours thoughts for decades! Not to mention losing me untold hours in fruitless Google searches. I really do thank you for taking the time and trouble to resolve this.
I'm almost positive that it was Maddock's 'The Time Maze' as you suggest and I've snapped up the one copy (!) available on Amazon. Now that the problem's solved I don't see how I didn't stumble across it myself after innumerable searches on 'maze', 'caves', labyrinths etc. etc. However, hitherto, for some reason, it was occluded from me - until now. Thank you so much again. JAW.

[Tab]

You're very welcome :)