12Persons serving again after retirement.N.I.
Where any person after retirement from service resumesF1. . . service, that retirement shall be left out of account for all the purposes of this Part of this Act except that—
(a)if a lump sum was granted on that retirement without any contribution being made, then unless that person on resumption ofF1. . . service, or within three months ofF1. . . marrying[F2 or forming a civil partnership] while again serving, refunds by way of contribution one half of the lump sum, no pension shall be granted to any[F1 widow, widower[F2, surviving civil partner] or child of that person]; and
(b)any lump sum granted on that retirement, less any refund, shall be set off against any lump sum to be granted in respect of[F1 that person's] service.
F2SI 2005/3325