I’m sure there are translations out there for most of them, but all I have is a facsimile of the 1780 edition complete with long-s and blotches from the printing press. Caveat lector: I don’t speak modern French (though I can read it slowly), never mind middle French or its variants, and I have no dictionary for it. So if you chanced to come here via Google looking for a translation - don’t use this one. Its accuracy is in no way guaranteed!
I sit here at my desk, surrounded by a monolingual Italian dictionary, a bilingual modern French one and the Oxford Latin Dictionary, with the Oxford English Dictionary open in another browser tab. None of these can help much with the real problem words (the verbs too short to have a recognisable stem and whose vowels are unreliable due to conjugation and unstable spelling), but they make hunting down hunches fun!
This is a sample of the French. It’s the easy bit - the opening.
En nun du Pere, du Fitz, e du Seynt Esprit, Amen. Nus Edward, einsne filz au noble Roy d’Engleterre, fesoms nostre testament, en nostre bon sen, e en nostre bone memorie, le Samedis procheyn apres la Pentecouste, e le an de nostre seygnur mil, deu cent, septsaunt secund, en certe manere. En primes, nus divisoms a Deu, e a nostre dame Seinte Marie, e a tuz seyns nostre alme; et nostre cors enseuelir, ou nos esseketurs, ceo est a saver, sire Johan de Bretayne...
In June 1272, Prince Edward was in Acre on crusade. A Muslim assassin infiltrated the stronghold and stabbed him seriously, possibly with a poisoned dagger - though that may well be a later embellishment, added so that we could have the pretty detail of his wife Eleanor devotedly sucking the poison from the wound. That is, presumably, the occasion on which he dictated this will. Details of wording like “we have had our seal set on this testament” rather than “we have set our seal” may suggest his weakness when this was written, which must have been rather frightening for a man who was so active and vigorous for most of his life. Apparently he never got around to making another will, even when he became king later that year and had a good many more things to “ordiner”. Perhaps it was on his to-do list - right after “subdue those Scots good and proper”.
In the name of the Father, and of the Son, and of the Holy Spirit, Amen. We, Edward, firstborn son of the noble King of England, make our testament, being in sound mind and memory, the first Saturday after Pentecost, in the year of our Lord 1272, in this manner. Firstly, we commit our soul to God, to our lady Saint Mary, and to all the saints; and our body to be buried where our executors, that is to say, sir John of Bretagne, sir William de Valence, sir Roger de Clifford, sir Payn de Chautros, sir Robert Tiletot, sir Otho de Gradisson, Robert Burnett and Anthony Bek, or any of them will have determined. To them we give and grant full power to ordain for the good of our soul, that all our assets, be they movable or not, be used in such a manner as to repay our debts, and redress the wrongs that we have done by our own hand or that of our deputies, and repay our people for their service, in a manner that seems good to them.
And because we know well that our belongings cannot suffice for this, we desire and permit that the abovementioned executors shall have full power, which we grant them as far as we are able, to order and manage all our lands in England, Ireland, Gascony and all our other lands, that they may hear from them in the same manner that we did when they were in our hands, without selling or giving them away, and together with them to hold the guardianship of our children until they should come to their full age, to carry out our testament and grants of charity in England, and then to do what our executors see is best to be done; to do these things, we designate a hundred thousand pounds.
And, after our bequests are made, and our alms-giving carried out, we desire that the revenues of the aforesaid lands be kept for the benefit of our children, and that they be delivered into the hands of the aforesaid executors, until the coming of age of our aforesaid children.
And, if by chance it happen that the our lord the king, our father, should die before the coming of age of our children (which God forbid), we desire that the realm of England, and all the other lands that may pass down to our children, be delivered into the hands of our aforesaid executors, together with our dear father the Archbishop of York, and sir Roger, and other upstanding men of the realm, that they may reach an agreement on any affairs that may arise, until the coming of age of our children named above, and that the revenues of the aforementioned lands be gathered and guarded by the hands of our aforementioned executors, and delivered to our children when they are of full age, to their benefit.
And furthermore we desire and ordain that two or more of our executors have the power to hear our accounts and receive from all our bailies, wherever they may be, since our departure from England.
And then, if they cannot prove that they have faithfully rendered each account, and if none of our bailies be dead, let his heirs be bound to render the account for him.
Regarding the dowry of our dear wife Eleanor, we desire that she keep in each detail everything that was so designated when we had the chance, and if these are not paid to her, we desire that she have everything that right and law will give her, according to the customs and laws of England.
And also we desire that where not all of our executors can go to see to the terms of this our testament, that four or more, in the name of the others, shall have the power for themselves and for the others to fulfil the aforesaid terms.
And to that end, we pray to our holy father the apostle, that he may see these terms kept, and enforced, and confirmed; and that he may pray for our dear father, that he may ensure that these things we have named be kept stable and firm across all of his realm and power, to the farthest reaches of the land.
In witness of these things, we have had our seal set on this testament, and we have begged sir John Archbishop of (Syria? Tyre?), and Vicar of the Holy Church of Jerusalem, and the honourable fathers, Brother Hugh de Revel, master of the Hospitallers, and Brother Thomas Bérard, master of the Templars, so that they also have set their seals to this document, together with our abovenamed executors in witness of these things that have been said.
Given at Acre, the Saturday abovenamed, the eighteenth day of June, in the 55th year of the reign of the king our father.
 ‘Edward I’. Nichols, John. A collection of all the wills, now known to be extant, of the kings and queens of England. London: Society of Antiquaries, 1780. Reproduced in facismile by Kessinger, 2007. 18-21. (Actually, it’s A COLLECTION of all THE WILLS, now known to be extant, of the Kings and Queens of ENGLAND, Princes and Princesses of WALES, and every branch of the BLOOD ROYAL, from the reign of WILLIAM THE CONQUEROR, to that of HENRY the SEVENTH exclusive. with EXPLANATORY NOTES, and a GLOSSARY. Why don’t we have titles that double as blurbs anymore? And it’s incorrect: Will’s will, such as it is, is included, as is that of Henry VII - but it was printed as an afterthought.)
 “tuz noz beyns, moebles e noun moebles” - I’m uncertain as to whether to translate “moebles” as “furniture”, but I think the sense is broader than that, to general movable possessions. I have to say I am very very tempted to translate “beyns” as “baths”. Clearly, Edward went native in Acre and tied up all his wealth in a very expensive exotic bath collection, some of them so large they would never be moved. This would explain the need to sell them off before returning to England, so that Henry III never has to know about his son’s shameful Eastern indulgences.
 “baliz”. In the absence of any helpful dictionary at all I decided to get creative and interpret this as a Frenchification of “bailies” (ie, bailiffs, men appointed to command or guard a stronghold/land in its lord’s absence). It was only after that it occurred to me that the word was probably French in origin anyway. The OED confirms this and suggests “baliz” would be an acceptable spelling; my modern French dictionary suggests that the only survivor is “bailleur” (sponsor, backer); my modern Italian dictionary gives “balia” (nurse, emphasis on the first syllable) and “balìa” (literary/obsolete, absolute authority or one to whom this was given, emphasis on -li-) and states that the second originates from Old French “baillie”. It gives no etymology for the first, which in itself suggests that it, like the vast majority of Italian words, comes direct from the Latin (”baiulus”, porter/carrier/bearer of a burden) and that Italian then later imported the “same” word with a different meaning from the French, keeping it alongside their own version. I love it when Italian does that. And I may well be alone in finding all this fascinating!
 “rendre a nostre gent’ lur servise” - I’m divided on whether this refers to formally paying the barons and other lords who followed him to Acre for their military service, or to paying off the gentlemen of his household, or possibly other servants - I’m not sure how specific the word would be with regards to class at this point.
 “en... ourir”: I can’t quite think of the English idiom, but I’m guessing it means ‘hear’ in the sense of hear pleas, receive messages, sit at the centre of the web - ie, order, run.
 I am very pleased with myself for working out that “le erceuesk de everwyk” is “the Archbishop of York”. For my next trick, I can even give him a name - Walter Giffard!
 “akondrunt” - I hereby make the executive decision that the first “n” should be “r”, because it makes more sense that way.
 The object of “receyvere” is left implicit - presumably messengers, or accounts, similar to “en ourir” above.
 The change from the plural to the singular is in the text. It isn’t clear whether he means the bailies or the executors, but logically the burden of proof would lie with the bailies.
 “ceo ke fust nome quant nus les pusams”. I think “pusams” must be the 1st person plural in the perfect indicative of “poer” (which seems to be the infinitive of “pouvoir” for this scribe, though it only occurs as a noun), and it makes sense grammatically, but it’s not clear whether he’s referring to some verbal agreement he made with Eleanor (or her relatives), or perhaps the contracts drawn up for the marriage.
 “a nostre seynt pere l’apostle”. Which apostle? The choice is yours! It could possibly be read as “seynt Pere l’apostle” (”pere” in the sense of “father” is spelt earlier as “piere”, so it’s not too great a leap), but that doesn’t explain the “nostre”. In itself “nostre” implies a prayer to Edward’s namesake saint, the Confessor - but he wasn’t an apostle.
 “Sur”. I don’t know enough about the theocratic and secular bureaucratic divisions of the Holy Lands at this point to know what the archbishoprics were, or even what “Syria” or “Tyre” was considered to be. But “Vicar of the Holy Church of Jerusalem” was surely a rather forlorn title by now!
 I think! On the entirely unscientific basis that “le disutime” just sounds like “the eighteenth”.