Threshold(?) seals advice please

[barrykellett99]

Here is my front door, with what i think is called a "threshold" under it? (the alu strip)


As you can see its a little gutter of about 8-10mm deep.
There is a serious draught getting in under the door.
I was looking at the Stormguard website as threshold sills for inward opening external doors. But nowhere have I seen any thresholds like this that is a gutter type thing. Was this finished as it should have been or is it missing half of its bits?

There is a weather Bar on the outside of the door but I can't see any old or remnants of any seals on the underside of the door.

I need to get this plugged ASAP before the proper cold weather comes in!