How to dismantle a down pipe that's fixed at both ends?

[BlockedUp]

I've a rainwater down pipe that is fixed at the gutter and attaches to a pipe that goes into the ground.
I need to dismantle it to remove a blockage near the ground.
I've removed several brackets and loosened the joints but still can't get enough movement to separate the pipes.
Do I need to use a long ladder and remove all the brackets / loosen the gutter fixings or is there a cunning trick I'm missing?
Thanks for your help.

 

[palaceray]

If it is a plastic pipe you could cut out a small section to allow you to clear the blockage and join it together again with a down pipe connector.
If it is cast you will probably need to dis assemble the entire thing.

 

[BlockedUp]

Thanks palaceray,

It's plastic.
Is it easier to insert a new connector than separate at the existing connectors?

 

[palaceray]

If you have got a ladder it should be easy to seperate the existing joints unless they are glued solid.

 

[BlockedUp]

The joints aren't glued as I can get the pipes to rotate.
The pipe is in three sections running from ground to eave.
As both the bottom and top are fixed I can't slide the pipes apart.
I've tried bowing the pipe out from the wall, but can't get enough movement to separate.