Overview: The Da Vinci Code, a fictional thriller by Dan Brown, and a film starring Tom Hanks, has re-popularized a number of real conspiracy theories concerning the Holy Grail: What is it? Why would the Church conceal what conspirators claim is a lie that could bring down the entire Christian Church?

The main conspiracy points put forward are outlined below.

1) Claim: Leonardo Da Vinci was aware of the resting place of the Holy Grail in his lifetime. He used a series of highly coded clues in his paintings to put forward his agenda that the Holy Grail was in fact the secret that Jesus and Mary Magdalen were married and that they had a baby. This was covered up by the Church, keen to suppress the role of women.

Evidence and arguments: The Da Vinci Code uses Leonardo Da Vinci's The Last Supper, painted on the wall of the Santa Maria della Grazie in Milan. The Bible says that all of the apostles were men. However, in the Last Supper, Da Vinci has left a strange V, feminine/chalice, shape between apostle John (who looks like a woman) and Jesus. The two figures seem to be joined at the hip. But, look again, is it a man at all? Is there the hint of breasts?

Does this imply the two had a particularly strong relationship separate from the other apostles? Some have even argued that it was a homosexual relationship.

V separating John (Mary?) and Jesus?

The character to John's right (Peter) is poking violently. Does this show that this figure is seen as an outcast of the group? Or is he pointing for further emphasis? Is the entire picture about this figure?

Enlargement of pointing Peter and John

Even more bizarrely, Peter (who didn't like Mary) is holding a dagger...

Peter and John (Mary?) with enlarged section, below, highlighted

Enlargement of Peter's right hand, holding a dagger

Confusingly, the figure looks remarkably like the Madonna of the rocks also mentioned in the Da Vinci Code.

The Virgin Mary in Leonardo's Madonna of the Rocks

Critics point out that Leonardo liked to paint androgynous figures. An example is this picture of John the Baptist:

Leonardo's John The Baptist has a more than passing similarity to the figure in The Last Supper

John The Baptist, added next to the Apostle John in the Last Supper

The Da Vinci Code argues that the letter V (for feminine, chalice or womb) is clearly visible between Jesus and the figure to his right. The letter M, marital, is also apparent...

The Last Supper (left section)

LVM possibly in the picture (probably others too)

Critics suggest another explanation for the apparent letters in the Last Supper. It's an alphabet soup! The initials of the official who commissioned the piece was LVM... You can read anything into it that you want.

2) Claim: The French term San Greal, the Holy Grail, is a term used in ancient texts, however, split the word differently, and you get Sang Real, this has a different meaning entirely...

Sang Real has been seen in ancient texts... Does this prove that they are the same thing?

Argument: According to The Real Da Vinci Code (UK Channel 4) it is a result of a simple transposition error in a 15th book by John Harding.

3) Claim: The Priory of Sion is a bone fide organization.

Dan Brown, in a forward to The Da Vinci Code, says:

This is also claimed in the book Holy Blood, Holy Grail by Michael Baigent, Richard Leigh, Henry Lincoln.

Argument: It doesn't exist. The Priory of Sion is a hoax. This was discussed in 'The Real Da Vinci Code' (UK Channel 4, Broadcast 3rd February 2005). The hoax was perpetrated, it was alleged in the programme, by three individuals with different agendas:

Gerard de Sède (a surrealist - who subsequently wrote a book exposing his part in this hoax - claimed he told the authors of Holy Blood, Holy Grail that it was a hoax while they were writing their book.)

Philip de Cherisey (who did it for fun).

Pierre Plantard allegedly did it to prove his claims that he was part of the Merovingian dynasty (ie a blood relative of Jesus and Mary) - he denies this.

According to Jean-Luc Chaumail, a journalist, the Priory of Sion was set up in 1956 by Plantard, named after a local hill, Sion les Mines.

4) Claim: They've found Mary and Jesus's child, Sarah. Margaret Starbird presented this in her book "The Woman with the Alabaster Jar". Mary fled to France (Gaul) and there was a child on board. Her name was Sarah. Sarah means princess in Hebrew.

Argument: 'The Real Da Vinci Code', UK Channel 4 said: Starbird may have misinterpreted the legend. The documentary shows a religious procession celebrating the boat arriving containing a Mary, however the two Mary's on board were neither Mary Magdalen. It is possible that the Sarah on board was the servant of the two Mary's. There is no real evidence Mary ever went to France, it is the stuff of legend.

5) Claim: The Da Vinci Code maintains that the final resting place of Mary Magdalen is under the pyramid at the Louvre, Paris. French president Mitterand, who oversaw the creation of this piece of architecture, was instrumental in ensuring that the pyramid has exactly 666 panes of glass (the sign of the devil). The pyramid is on The Rose Line which is the original line of world time, the Rose is another name for the Holy Grail.

6) Claim: Da Vinci Code: X-rays of the Mona Lisa show she was originally painted with a lapis lazuli pendant of Isis. This means that she was originally seen belonging to one of the groups who knew of the Holy Grail's secrets.

7) Claim: Da Vinci Code: The last grail sighting was in 1447. Numerous eyewitnesses described a fire which had broken out. The documents were carried to safety in four huge chests which each required six men to carry.

8) Claim: The mountainous backdrop of Madonna of the Rocks matched topography of a series of cave ridden hills in Scotland. This was a clue to the hiding place of the Holy Grail.

Is it really possible to identify the rock formations in this picture, Madonna of the Rocks?

9) Claim: Rosslyn Chapel, Scotland, has substantial underground burial chambers which we know exist but have not been seen since they were sealed. Conservationists refuse permission to dig up the church for a full investigation. Could Mary be resting here? In Dan Brown's book this place is the subject of a plot point which we won't detail here as it spoils the story. The church, however, has various iconography in the walls and is a popular destination for Holy Grail enthusiasts..

Argument: In real life: The vaults under the chapel have not been investigated so it can't be proved either way, although it was said that during the time when these vaults were open to relatives, nothing was noted out of the ordinary.

10) Claim: Who compiled the bible? Was it an attempt to control society? and specifically to control the position of women in society? It is alleged that whoever compiled the New Testament chose 27 books, we know there were more books than this, the rest were hidden. They were discovered in December 1945 Mohammed Ali es Samman - Known as The Gnostic Gospels. Some of which claim to be the actual teachings of Jesus.. In the newly found Gospel of Philip: "Jesus kisses Mary on the lips"...

Argument: Nothing in these documents says Jesus and Mary were married. The Gospel of Philip doesn't say Jesus kissed Mary on the lips. The scroll says 'Jesus kissed Mary on the' then it stops as there is damage to the scroll... experts imply it is the lips.

11) Claim: It would have been very unusual for Jesus, a Jew, to not be married at this time in history.

Argument: Jesus was an unusual man. He spoke up for the poor in society, itself a strange thing to do at this time.

12) Claims about the Mona Lisa (La Joconde) in the book:

a) The background behind her face is uneven; Da Vinci painted the horizon line on the left significantly lower than on the right. This makes Mona Lisa look larger from the left than on the right.

The top part of the Mona Lisa, supposedly showing the horizon line significantly lower on the left.

b) Da Vinci was a fan of feminine principles, he made her look more majestic from the left than the right

Does the image on the left look more feminine?

c) Mona Lisa is Da Vinci in drag. Computer analysis of Mona Lisa and Da Vinci self portrait(s) confirm 'some startling points of congruence'.

We have flipped Mona Lisa horizontally and adjusted her to match the pose of Da Vinci in this self portrait. Are they the same person?

d) AMON (God of Fertility) L'ISA (corruption of Isis - Egyptian goddess of fertility) - Reason for Mona Lisa's smile...?