Secret Bible which predicts coming of Mohammed discovered by Daily Mail...

Secret Bible: The 1,500-year-old tome was is said to contain Jesus' early teachings and a prediction of the Prophet's coming
The Daily Mail has recently published an article that has the Muslim blogging community buzzing with excitement and self-righteousness.
The article claims that the "secret Bible", which has been "rediscovered" in Turkey, predicts the coming of Mohammed and denies the Trinity and the crucifixion of Jesus. (The Qur'an states that Jesus was a prophet and not the Son of God, that the Trinity is a pagan heresy and that Jesus wasn't crucified but was taken up to Heaven alive and someone else put on the cross in his place.)
This "Bible", it turns out, is a version of the Gospel of Barnabas -  which is known to exist in two copies which date from the 16th century. Wikipedia has this to say about the Gospel:
The Gospel of Barnabas is a book depicting the life of Jesus, and claiming to be by Jesus' disciple Barnabas, who in this work is one of the twelve apostles. Two manuscripts are known to have existed, both dated to the late 16th century and written respectively in Italian and in Spanish—although the Spanish manuscript is now lost, its text surviving only in a partial 18th-century transcript.

It was also mentioned in 1734 by George Sale in The Preliminary Discourse to the Koran:
The Mohammedans have also a Gospel in Arabic, attributed to St. Barnabas, wherein the history of Jesus Christ is related in a manner very different from what we find in the true Gospels, and correspondent to those traditions which Mohammed has followed in his Koran. Of this Gospel the Moriscoes in Africa have a translation in Spanish; and there is in the library of Prince Eugene of Savoy, a manuscript of some antiquity, containing an Italian translation of the same Gospel, made, it is to be supposed, for the use of renegades. This book appears to be no original forgery of the Mohammedans, though they have no doubt interpolated and altered it since, the better to serve their purpose; and in particular, instead of the Paraclete or Comforter, they have, in this apocryphal gospel, inserted the word Periclyte, that is, the famous or illustrious, by which they pretend their prophet was foretold by name, that being the signification of Mohammed in Arabic; and this they say to justify that passage in the Koran where Jesus Christ is formally asserted to have foretold his coming under his other name Ahmed, which is derived from the same root as Mohammed and of the same import.
"Ah, but you are taking a very Judeo-Christian view of this discovery", Muslim apologists will say. So let us turn to an apparently academic study of the Gospel of Barnabas by a German Muslim specialist at the IslamInstitut, Prof., Dr. Christine Schirrmacher, Academic Director of the Islamic Studies Institute in Bonn
Dr Schirrmacher seems to be fairly dismissive of the gospel for the following reasons:

In the Gospel of Barnabas, the command is given by God to Mary and Joseph to keep Jesus away from wine, strong drink, and impure meat —that is, pork: the prohibition of pork and wine is, however, an Islamic prohibition, not a Christian one.
In the Gospel of Barnabas, Jesus announces the coming of Muhammad and already speaks the name of Muhammad. Jesus asks God to send Muhammad to save the world. In Jesus’time, no one knew that, six centuries after Jesus’ death, Muhammad, on the Arabian peninsula, would claim to be sent by God and to preach the truth. In the Christian view, it is impossible that Jesus announced Muhammad and asked God, his father, to send Muhammad Also inconsistent with the Koran is the oft-repeated statement in the Gospel of Barnabas that Muhammad is the Messiah, while it at the same time repeatedly denies that Jesus is the Messiah. It characterizes Jesus, however, as “chrissto” (Christ). The assumption, therefore, is that the author did not know that “Christ” is the Greek equivalent of the Hebrew word for “Messiah” (“the Anointed”).
The Gospel of Barnabas itself stresses that the original Biblical gospel was falsified. If Barnabas actually would have been a contemporary of Jesus, then the formation of the New
Testament would not yet have been concluded. With this statement, the Gospel of Barnabas would have forecast its own fate. In addition, his geographical and historical mistakes make clear that the author of the Gospel of Barnabas can neither ever have visited Palestine nor can he have lived in the first post-Christian century In the Gospel of Barnabas, Nazareth is a town on the shore of the Sea of Galilee. Nazareth,however, stands upon a hill some distance from the Sea of Galilee. According to the report in the Gospel of Barnabas, Jesus ascends from the Sea of Galilee to Capernaum. Capernaum, however, lies directly on the shore of the Sea of Galilee. According to the description in the Gospel of Barnabas, Nineveh lies near the Mediterranean coast. It, however, is to be found in the interior on the banks of the Tigris.
The editors of the first Italian-English edition of the Gospel of Barnabas, Lonsdale and Laura
Ragg, in addition, point to conspicuous parallels between the Barnabas gospel and the works
of the great Italian poet Dante Alighieri (1265-1321), such as La divina commedia (The Divine Comedy), and, in particular, to Dante’s representation of Heaven, Hell, and Paradise.So, for example, the number of nine or, including Paradise, ten heavens, as well as the subdivision of Hell into seven centers in the Gospel of Barnabas agrees with Dante’s discussion of the ten heavens...The most probable date of composition of the Gospel of Barnabas lies, for Lonsdale Ragg, between 1300 and 1350 Subsequent investigators have expanded this time span to aslate as the sixteenth century.
So what of the idea that this is a secret gospel, hidden from the public by embarrassed Christians? Let us turn to the professor again:

The endorsement of this gospel’s authenticity always goes hand in hand with the Muslim claim that the Christian church has attempted to conceal this true gospel from the public. The opposite, however, is the case: the first efforts to produce a complete text of the gospel were made by Christians in 1907. Since this time, the Gospel of Barnabas has been available in a number of languages. No one in Europe had any interest in a new apocryphal text before the increase of Muslim statements in favor of the gospel.
In conclusion then, what we have is another attempt by Muslims to try to lend authenticity to their religion by dubious, not to say, underhand means.
Muslim Educational Trust (MET) LAHORE (no date)
A typical miracle seekers attempt to convince readers that the Gospel of Barnabas is ancient and was found among the Dead Sea Scrolls

Post script: For those interested in how the Muslim miracle seekers lie to their own followers and to anyone else gullible enough to swallow their rubbish, here is a site sponsored by the Sabr Foundation all about how the Gospel of Barnabas is a genuine Gospel dating from the first century.