Support for Purlins

I am in the process of extending the floor area of a room in my house into the loft space.
Below is a drawing of the current state of the room. The key to the colours is as follows:

Yellow...Purlins
Red... Floor Joists
Green...2" Angle Iron

The Angle iron will need removing at some point as it is obviously in the way.
It seems to have been put in to support the Purlins for some reason.
It is a later addition to the house and it is attached to the floor joists but the bolts go through the floorboards first.

Can someone explain the possible reasons as to why this was fitted.

My reasoning is as follows.

The room was originally one room as shown, but was later divided into two
at the point where the angle iron runs. I think that the door way shown was created at this point to provide access to one of the rooms. Since the purlin rested on the wall where the door way was created, this reduced support for the purlin. Although there is a wooden lintel over the doorway, it doesn't look very substantial. Therefore, the angle iron arrangement has been made to provide further support for the purlin. Does this sound right?

I would be bricking up the doorway as the original entrance on the other wall will provide access to the room. Would this restore satisfactory support to the purlin allowing removal of the angle iron?

Thanks for any help.

You'll need a structural engineer and Building Regs Approval.

It looks like the angle from the high purlin is a hanger to support the angle iron on the red joists which is acting as a binder.

The angle iron to the lower purlin looks like it is functioning as a post with a further supporting raking piece of angle iron

I've had a builder around to have a look at this.

The red floor joists have been notched to accomodate a waste pipe. This has been done right in the centre of the span on the top surface.

The angle iron is acting as a binder as Woody explained.