Children's / YA novel and game about travelling back in time via an old tree

Question

I'm looking for a book I read back in school, probably in the period 1991-1996. What I remember of the book is:

• I think it's set in Sydney, Australia
• The main characters are a boy and a girl
• There's an old tree that's going to be cut down, and they're collecting signatures for a petition to save it
• They wind up going back in time - I think there's a tunnel in the roots of the tree that takes them back
• I'm pretty sure they go back to early colonial Sydney, and probably befriend a child of their age from that period
• The tree had a distinctive name, which I think was in the title of the book

There was also a computer game adaptation of the story that I played on the school computer.

• It was an interactive fiction game, with commands entered in the typical " " style (e.g. "look", "pick up rock", "go east")
• I remember there being primitive (monochrome) graphics but it's quite possible I imagined them - if they actually existed, then they were still images of the location you were at rather than being a map or anything similar
• The first part of the game has you going around talking to people to collect the signatures
• When you find the tunnel, you have to navigate it by following a light and the description is either something like "the light of the guides you to the north" or "you can't see the light of the " depending on whether you've gotten lost or not

I know that we had MicroBee computers as well as Apple IIe ones at various points, so it might have run on one of those, but there's also a small chance it was a DOS title so unfortunately that doesn't narrow it down much.

Answer 1

This is almost certainly "The Riddle of the Trumpalar Tree" by Judy Bernard-Waite (goodreads link).

Matches:

• Australian, the description on Goodreads doesn't specify which city
• Main characters are 11 year old twins
• petition to save an old Moreton Bay fig tree
• the main characters 'enter' the tree, and meet its guardian
• the tree does, indeed, have a distinctive name.
• published 1981, so able to be read in the early nineties

Uncertain of match:

• time travel

The book also has a sequel, Challenge of the Trumpalar, which does feature time travel to the past, which may be the one you are thinking of, but that was published in 1996, so is only just on the edge of your timeframe.