Can anyone identify these old TV series?

[trevmds]

Can anyone identify these old English TV series from the 70s?

1) Two kids (boy & girl) find invisible portal that tales them back to a WWII army base. Occasional studio sequences with presenter demonstrating alternate time-travel theories using props etc.

2) Moonbase colony. One episode was about them thinking that Earth had suffered nuclear armageddon, as they'd lost contact, and the whole planet had been covered in a blanket of cloud, but it turns out at thje end that it's just freak weather conditions.

And to make this on-topic, do they still exist?

[C Jordan]

The first is 'Timeslip', the second is the last episode of the BBC series 'Moonbase three'.

These both still exist, but the Timeslip story probably only exists in B/W now.

Moonbase Three was thought lost for a long while until NTSC versions turned up in America. This is currently available on DVD.

[Harry]

...and Timeslip was released on VHS in the 1990s in it's entirety. A DVD is long overdue.