the passage is dangerous and subject to interception
∪ = a · 7 = e · z = o · + = b · ∞ = d · V = r

Ostend → Walsingham · substitution cipher of graphic signs within clear English · 20–22 March 1587/8

Lord Cobham at Ostend to Walsingham, 20–22 March 1588

Lord Cobham
fromLord Cobham
Francis Walsingham
toFrancis Walsingham

British Library, Harley MS 287 ff. 70–72 (DECODE R8482–R8487), catalogued as seven ciphertexts of an unknown sender to an unknown recipient. They are two signed letters of William Brooke, Lord Cobham, written from Ostend during the 1588 peace talks with Parma, and a cipher enclosure from Middelburg. The cipher is a simple substitution in graphic signs. No decipherment was found on the leaves or in print; the key was recovered from the clear English around the cipher runs, and most runs are deciphered. About a third of the runs on f. 70r and a few names stay open.

Daniel Bourdeau · posted · updated

Method: key recovered based on adjacent plaintext · Extent: partial

Summary. Item 132 of the catalogue listed seven DECODE records from Harley MS 287 with no sender, recipient or decipherment. Six of them (ff. 70r–72v) are two letters of Lord Cobham, one of Elizabeth’s commissioners for the peace talks with the Duke of Parma, dated at Ostend on 20 and 22 March 1587/8 (Old Style) and signed “your assured loving friend H. Cobham”, with an intelligence report from Middelburg between them. The addressee is not named; the volume and the content point to Walsingham. The cipher runs sit inside clear English, and there is no decipherment on the leaves and none was found in print. The clear words gave the cribs (“commaunded to attend”, “that bearer hath”, “under colour thereof”), and the key is a simple substitution in graphic signs, with a few homophones and the words divided. The deciphered runs report Parma’s new canal from Ghent by Eeklo to Sluys “within 15 days navigable”, his build-up at Oudenburg, a garrison “too weak by the half” with five weeks’ pay left, the prisoners Pigot and Barney, Cobham’s lack of spies, and his refusal to be “a means to conclude an irreligious peace”. A few dotted numbers and a square are nomenclator signs: 15 is Parma, □ the States, .7. probably the Queen; 42 is not identified. The seventh record (f. 11) is a different letter in a different code and is not deciphered.
Harley MS 287 f. 70v, the head of Cobham's letter of 22 March 1587/8, with the cipher runs in the clear English
f. 70v, 22 March 1587/8: “This preparation, together with the reinforcing of his garrisons hereabout”. Image: British Library, Harley MS 287 f. 70v, via DECODE R8483.

01 The documents

DECODEFolioWhat it is
R8482–R8483ff. 70r–70vCobham, Ostend, 22 March 1587/8.
R8484f. 71rIntelligence “from Middelburgh”, another hand: Grenier’s schemes, a Latin tag, five lines of cipher.
R8485–R8487ff. 71v–72vCobham, Ostend, 20 March 1587/8, signed on f. 72v.
R8477f. 11An undated, unsigned intelligence letter in English about a Spaniard and the Spanish agent, with one line of numeral and letter code groups. A different system; not read.

The Commission (Derby, Cobham, Croft, Dale, Rogers) reached Ostend in March 1588. The letters name Mr Controller (Croft), “Mr Doctor Rogers” being sent to the Duke at Bruges, and a servant of Lord Burghley, all in clear. The Calendar of State Papers Foreign calendars Cobham’s letters of 22 and 24 March to Burghley, from the State Papers, but not these. The key on f. 187 of the same volume (R8497, Bodley, 1590) is a different system.

02 The cipher

Each run replaces the letters of English words with signs, one sign per letter and the words kept separate. A few letters have two signs (a: ∪ and ⊥; w: two dots and a dotted x; g: a barred x and a 3), and a colon after a letter stands for u. The signs of one family (l, p, h, m, all drawn as a crossed or looped stem) and the two carets for s and t are close on the scans; they were settled word by word.

abcdefghilmnoprstu/v/wy
∪ ⊥+8∞7H̅Ӽ 3ϵ⊥ϕ∝††zϕV∧∧.. ẋɣ

The key was rebuilt from the clear words on either side of each run. A session working on Cobham’s May–June letters in the same volume then found the same values in the contemporary glosses of f. 89 (R8493).

03 The decipherment

Deciphered words in italics, modern spelling. Grades as in the README: (C) supplied from context, (M) uncertain; the rest is high.

22 March, ff. 70r–70v

What effect this message will work I know not, but doubt the worst, and therefore do wish and think it expedient that some of .7. ships were commaunded to attend on this coast for all events, for I am persuaded 15 will never yield to send 42 hither. Some provision also for vittailes would be necessarily thought upon, for □ have no megasines here, nor mind to have any. That the same here is but from weeke to weeke as the bilanders do voluntarily bring it … there is any money stirring here. The present garrison will be found too weake for the defence of so large a circuit by the half at the least. The last supply of money will not [keep them] from the presentes wantes of the souldiers above five weeks longer, as the governour tells me. … The Duke is expected within a day or two to be at Bruges. The newe ditche from Gaunt by Eecloo unto Sluce is said to be almost ended, and will be within 15 dayes navigable for the float boates and vessels he hath ready prepared, being some of them fraught with stones and fagottes.

This preparation, together with the reinforcing of his garrisons hereabout, Stanley’s repair unto Turnhout (M), make such [at] Oudenburgh with eleven companies of footmen, and the Duke’s coming to Bruges doth threaten somewhat (C). And in mine opinion this town is fit to be stopped (C) through some attempts upon the haven; which being once stopped, the town being already abandoned of succour by land, cannot make resistance against the enemy many days (C) together.

My greatest grief is that in all this town I am not furnished of any one spy to employ abroad for the more certainty of the enemy’s proceedings. And from Flushing I hear very seldom by reason that the passage is dangerous and subject to interception. … By my servant William I wrote in my private letter a special motion for our remove to Flushing (C), where we might better stand on terms for her Majesty’s honour.

Middelburg report, f. 71r

In my opinion the ships would be well guarded (C), and when all ships of charge as well of the [fleet] as merchants be at sea (C), there would be 2 or 3 pinnaces appointed to [watch] and direct the channel (C). [Bastune?] the Jesuite is within these fewe dayes sent post into Italy (surname M). R. tould me in talke with him that 15 ha[th] [in]sted his sonne (being under 17 years of age) in the government of his patrimony in Italy.

20 March, ff. 71v–72v

There are new companies lately added to the old garrison of Oudenburgh, our near neighbours (C), which were very strong before. This drawing of his forces by land so near, and the provision of stone and fagots to come from Eecloo by water (C), make us suspect some attempts against this town and haven: we think it therefore expedient that some of the ships did continue upon this coast, to be ready for service upon occasions. Also we pray your honour (C) would remove us hence or dismiss us to some other place of more surety (C).

This bearer hath laboured his own dispatch and would fain have had instructions, but I, fearing that under colour thereof he would proceed in his charge, did let him understand what we had generally written unto my Lord … As by the [words] of your own hand in your letter of the 16 March I perceive you oppose yourself still against such resolutions; for mine own part I would think myself most unhappy to be a means to conclude an irreligious peace. Touching Pigot and Barney, if they shall be delivered over to the States, I am of another opinion … things standing as they do, □ will ranson them, and then what dishonour and disfavour will it be for her Majesty. Pigot is a martial man, and hath means and will to deserve his prise (C).

04 What stays open

05 Sources

Notes, key and profile: harley287/ in the repository.