Leech and Grappling Clarification

[Dalren]

I'm looking for some clarification on when the HP drain from Leech actually occurs. Here's the relevant info from Powers.

Originally Posted by Powers pg. 96

To use Leech, you must maintain
ongoing contact with your victim; a
brief touch isn’t enough. In combat,
you must grapple or pin him – which
is trivial if he’s unconscious or otherwise
helpless.

Originally Posted by Powers pg. 96

While you maintain contact, each
level of Leech lets you drain 1 HP per
second from your victim.

Assuming you start the turn without being in contact with the target, you would need to roll against DX or a grappling skill (using Attack, All-Out Attack, or Move and Attack) to initiate the grapple.

Originally Posted by Basic Set: Campaigns pg. 370

Each attempt requires an Attack,
All-Out Attack, or Move and Attack
maneuver. Roll against basic DX or a
grappling skill to hit.

If your roll succeeds, your target then gets to defend as they would against any other attack.

Originally Posted by Basic Set: Campaigns pg. 370

Your foe may defend normally –
he can parry, dodge, or block.

If your target fails to defend, does the drain from Leech occur immediately or do you need to have the target already grappled at the beginning of a turn on which you want to drain? That is, do you start the drain as soon as the grapple connects or does it not occur until you've held the grapple an entire turn (giving the target a turn in between to break free)?

[Nereidalbel]

The turn after the grapple succeeds. Do note that bolas, nets, and Binding Attacks make this easier.