In P & O Nedlloyd BV v Arab Metals Co & Anor  EWCA Civ 1717,  1 WLR 2288 the Court of Appeal held that, where an appeal set aside an order below, the judgment appealed from was a nullity, and the findings on which it was based could not found an estoppel as between the parties. Thus said More-Bick LJ:
29 ... Issue estoppel is a form of estoppel by record and depends ... on a decision of the court disposing of a substantive dispute between the parties. On a purely formal level it may be said that the setting aside of the order below expunges the only record from which an estoppel was capable of deriving its force. At a substantive level the setting aside of the order means that there is no longer any disposal to which the decision on the issue in question can be regarded as fundamental.
The decision in W v H (orse Sharbatly v Shagroon)  EWHC 3756 (Fam) turned on the ruling in P & O Nedlloyd BV. The Court of Appeal had earlier held ( EWCA Civ 1507,  1 FLR 1493) that a woman's marriage which was not performed under the Marriage Acts could not be a marriage at all (and could not therefore be void, even under Matrimonial Causes Act 1973 s 11). The High Court had had no jurisdiction to entertain an application under Matrimonial and Family Proceedings Act 1984, Part III. The first instance decision of a deputy judge in 2012 under Part III was therefore set aside.
Further, in earlier proceedings concerning return of children to Saudi Arabia, alongside the nullity proceedings in 2002, the parties had settled those proceedings on terms that included that H undertook to provide financially for W and the children. W claimed in 2013 that H had breached that undertaking. With no obvious surviving family proceedings she applied for a variety of financial provision including ‘specific performance of undertakings' and ‘capitalisation of other liabilities' (Paras  and ). The judgment now under review predated any disposal - perhaps still awaited - of those applications. W wanted to rely on certain of the deputy judge's findings. Was she in law entitled to do so, where his judgment had been set aside on appeal?
Once P & O Nedlloyd BV (above) was drawn to W's advisers' attention she agreed to abandon her reliance on the deputy judge's findings. So who should pay the costs of what Parker J called the ‘determination of the estoppel argument' (para )?
Parker J held that she did not need to decide which procedural rules applied. Even if these proceedings were for enforcement only, they would be family proceedings and the court starts with a ‘clean sheet' (few judges whose decisions are reported seem to be referred to Gojkovic v Gojkovic (No 2)  Fam 40,  2 FLR 233, CA: namely, that ‘costs follow the event' is a good starting-point). However, she was deciding ‘a discrete preliminary issue':
 ... So I do not need to decide whether W's proceedings are properly to be regarded as solely or mainly civil proceedings to which the whole of CPR Part 44 applies.
 In that context, I do not think that it makes any difference whether I approach the decision from the standpoint of CPR Part 44 or on the basis of the clean sheet.
This is the ratio of the case.
The other interesting points might be thought to be: the discussion of issue estoppel following a set aside order (not a variation or remission for redetermination: CPR 1998 r 52.10(2)); and the, as yet, unresolved question of how W pursues her undertaking argument. In reality, must this be pursued in contract and, if so, when does any limitation run against her (one of the issues, as it happens, before the Court of Appeal in P & O Nedlloyd BV)?
David Burrows, solicitor advocate, is author of Practice of Family Law: Evidence and Procedure (Jordans, 2012). Costs are dealt with in Chapter 13.