UK - France capital gains on property

I have a client who is resident in France but owns and rents UK property. He moved permanently  to France in 2007 but has owned the property portfolio for some time before that. He has asked me what the UK CGT situation will be if he sells a property.

Looking at HMRC CGT manual CG12600 it says

Persons, including companies, are not chargeable to tax in respect of chargeable gains if, in the year of assessment or accounting period in which the disposal is made, they are neither

• resident nor, in the case of a person other than a company, ordinarily resident in the UK, nor
• non-resident and in the case of a person other than a company carrying on a business in the UK through a branch or agency, see CG25500+, nor
• non-resident and in the case of a company carrying on a trade in the UK through a permanent establishment, see CG42100+, nor
• associated with exploration or exploitation activities in a designated area of the continental shelf.

However Article 14 of the latest Double Tax Treaty says

Gains derived from the alienation of immovable property referred to in Article 6 and situated in a Contracting State may be taxed in that State.

There is of course the MAY in the latter article but I am assuming if a state may tax something it usually will.

So the law seems to say the person is not taxable but the asset is. Which applies in practice ? I appreciate he will not be taxed twice under the DT treaty but I do not know if he would need to make a UK CGT declaration and pay CGT to HMRC.