Theme Will Tear Us Apart Again

But in Halliday ± Matthiessen (1985, 1994, 2004, 2014), in cases of predicated Theme, the embedded clause is also analysed for Theme:

Encoding Clause With Theme Predication Vs Existential Clauses

it	was	John	[[who painted the shed]]
Theme: predicated			Rheme
Sub-	Finite	Complement	-ject
Val-/Ident-	Process: identifying	Token/Identifier	-ue/-ified

there	was	John [[who painted the shed]]
Theme	Rheme
Subject	Finite	Complement
	Process: existential	Existent

perhaps	there	was	one [[who didn’t lecture]]
Theme		Rheme
mood Adjunct: modality	Subject	Finite	Complement
		Process: existential	Existent

Predicated Theme Vs Postposed Subject

it	‘s	your good luck	that	nobody	noticed
Sub-	Finite	Complement	-ject
Identi…	Process	Identifier	…fied

Ambiguously:

(a) Predicated Theme (agnate to nobody noticed your good luck)

it	‘s	your good luck	that	nobody	noticed
Theme: predicated			Rheme

(b) Postposed Subject (agnate to the fact that nobody noticed is your good luck)

it	‘s	your good luck	that	nobody	noticed
Theme	Rheme		Afterthought

See Halliday & Matthiessen (2004: 97-8).