In the preface to the Arcana Aulica Walsingham is described in 1652 as one who, "though very young, in a little time grew up, under the wings and favour of the Lord Digby, to such credit with the late king that he came to be admitted to his greatest trusts, and was prevented only by the fall of the court itself from climbing there into an eminenter height."
On 31 October Digby was made high steward of Oxford University, and through his influence Walsingham was created M.A.
In 1652, he was involved in a Catholic intrigue to remove Hyde from Charles II's service, but for some reason he revealed the scheme.
In 1654 Walter Montagu made him a companion to Henry Stuart, Duke of Gloucester; but later was excluded from his company.
At the Restoration, he remained in France, acting as secretary to Walter Montagu, who was abbot of St. Martin's, near Pontoise.
[9] In 1651 he sent as a present to Ormonde his Arcana Aulica, or Walsingham's Manual of Prudential Maxims for the Statesman and the Courtier.
Its original was an anonymous French work, Traité de la Cour, ou Instruction des Courtisans, by Eustache du Refuge, a diplomat and author in the reign of Henry IV of France.
In 1694 it was issued with Sir Robert Naunton's Fragmenta Regalia in 1722 an edition was published substituting Instructions for Youth for the first part of the title, and giving different renderings of various passages from classical authors (reprinted 1728).