The Great Seal  (see examples below)
The principal Seal of Royal Authority.  Used to authenticate signatures and documents of the highest importance and began with Edward the Confessor and used to fix a double hanging seal to a writ sent to Leofwane, Bishop of Eadwine Earl, and his thanes in Staffordshire.  For over 400 years every message sent by the King was sealed with his personal Great Seal or "The Key of the Kingdom."  A new seal is created for each monarch. In bygone days the seal of the dead Monarch was broken by the newly enthroned Monarch and the silver, of which the seal is made, was broken down and passed between the poor.  Today, the seal is ceremonially broken by lightly tapping it with a hammer so as not to damage the engraving and handed to the Lord Chancellor who is its keeper.   

The Seal is always round and made of silver and up to six inches in diameter.  It is not a medallion but a mould made in two halves.  Softened green or red wax is placed in each half of the mould and the halves are pressed together. Excess wax is shaven off and the waxed hardened in cold water.  The wax impression (Seal) is attached to a document by strings or "laces".  The Seal is used less often today but used it is eg, when Royal assent is given to the election of a Bishop or Archbishop or when power to sign and confirm treaties is given. To protect the wax impression of The Great Seal it is tied in a woollen or silk bag. The Seal itself was protected in a finely decorated bag and placed in a box made of solid silver; today it is held in a japanned iron box.  

Wax is always used as the medium for the impression although there have been exceptions.  In 1213 King John made a Seal of gold to be attached to the document that gave his realms of England and Ireland to the Pope. Another, again of gold, hangs from the document confirming the Treaty Henry VIII made with Francis I of France. 

The Seal is held in such high regard that an office of Gentlemen Servants in Attendance was created to tend the Seal. Until 1832 these attendants were known as:

The Clerk of the Hanaper.  A hanaper was a hamper holding documents for sealing.  The Clerk took charge of the money for the use of the Great Seal and he had an apartment in the Palace of Westminster for himself. His wax, clothing and parchment was also given to him.

The Spigurnel (Sealer). He had to be on duty 24 hours a day and never took a holiday. He was given an allowances for towels to clean away the excess wax from The Seal, for escorting the Seal around the Country and for four large red cloth bags used to transport the Seal. At one time The Chaffwax was kept as a servant called The Portjorie who kept the Sumpter-Horse which was used to carry the books and parchment rolls.

The Chaffwax (who prepared the wax for the Seal).

The Porter (who transported the seal from one place to the other).

The Purse Bearer (who carried the purse containing the Seal). In 1832 saw the above positions disbanded and The Purse Bearer carried out the work of all of the above for a fine annual salary of an extra £100.  The Purse itself should not be confused with the small ladies purses and wallets we carry in handbags and back pockets.  The Great Seal was up to 6 inches in diameter and made of silver and very heavy.  The Great Seal is the mould for making the wax impression and had to be protected. The purse in which it was held was replaced each year and finely made. An invoice from Roger Nelham, maker of the purse in 1652, included the following description "embroidering the rich purse for the Greate Seale of England with best double refined gold and silver upon a rich velvet, ingraine with the arms of the Commonwealth of England at large" The purse was always given to the Chancellor's wife. One Chancellor's wife acquired so many purses that she used them to make curtains.  Until 1882 the ritual of a new purse each year continued until the death of Elizabeth Berry. From then on the purse was used until it wore out and another made.  The Lord Chancellor carries the Queen's Address within the purse whilst in procession at the State Opening of Parliament

Below are examples of Great Seals of England, most have the reverse and obverse aspects of the impression.

The Lord High Chancellor of Great Britain (Lord Chancellor) and in former times Chancellor of England, is one of the most senior and important functionaries in the government and custodian of The Great Seal.  He is the sixth senior in rank of the Great Officers of State, and is appointed by the Sovereign on the advice of the Prime Minister. He is by convention, always a peer, although there is no legal impediment to the appointment of a commoner. The Lord Chancellor's responsibilities are wide-ranging and include presiding over the House of Lords,  participating in the Cabinet and heading the judiciary.  When he leaves office he "gives up the key".  During the Middle Ages the Chancellor was the King's Chaplain and wrote the King's letters and of course Keeper of the Seal, which was called The Great Seal to distinguish it from other smaller seals.   

Seal of Alfric, Earl of Mercia

King Alfred's Jewel.  

In 1693 a jewel was unearthed near to the Isle of Athelney, where King Alfred took refuge from the Danes in 878.  A Saxon inscription around the edge reads 'Alfred Had Me Made'.  There are many theories regarding the purpose for which the jewel was made. Here are a few: (1) The handle of a pen; (2) The handle of a page turner, used to keep dirty hands from touching valuable bibles (3); The head of a sceptre; (4) A pendant. 

Great Seals of Edward the Confessor

Great Seal of William the Conqueror

Great Seal of William Rufus

Seal of Milo Fitz-Walter, Constable of England under Henry I

Great Seal of Henry I

Great Seal of Stephen

Seal of Richard, Constable of Chester in the time of Stephen

Great Seal of Henry II

Great Seal of Richard I

Great Seal of King John

Seal of King John to the Agreement with the Barons and found on the Magna Carta in 1215

Conventual Seal of Rochester

Great Seal of Henry III

Great Seal of Edward I

Great Seal of Edward II

Great Seal of Edward III

Great Seal of Richard II

Great Seal of Henry IV

Great Seal of Henry V

Great Seal of Henry VI

Great Seal of Edward IV

Great Seal of Richard III

Great Seal of Henry VII

Great Seal of Henry VIII

Great Seal of Edward VI

Great Seal of Mary I

Great Seal of Elizabeth I

Great Seal of James I

Great Seal of Charles I

Great Seal of the Commonwealth.  It was designed by Thomas Simon and struck in1651, 5.5 inches in diameter, and was so highly crafted that the name of each county can be read on a map of the British Isles.

Cromwell's Great Seal for Scotland
 

Great Seal of Richard Cromwell

Great Seal of Charles II. When Charles II was restored as Monarch he ordered James Simon to design a new Seal.

Charles carried a plainer Seal when a 23 year old he marched his Scottish soldiers towards Worchester. After his defeat in battle he threw the Seal into the River Severn in case Cromwell's men took it. It was never found.

Great Seal of James II.  James attempted to leave the Country in 1688 when his attempts to force Catholicism on England. As he was rowed along the Thames in company with Sir Edward Hales he carried the Great Seal in his pocket. As he approached Lambeth Bridge the King threw the Great Seal into the waters in the belief that without it the Government could not carry on. The Seal was netted by a fisherman at Vauxhall. He took the Seal to the Lords of the Council who handed it to William of Orange. William and Mary used it until 1689 when the new Seal showing both Monarchs was completed. James II's abdication was dated from the date that he threw The Great Seal into the Thames which was 11 December 1688. 

Great Seal of William and Mary

Great Seal of William III

Great Seal of Anne (before the Union with Scotland)

Great Seal of Anne (after the Union of England and Scotland)

Great Seal of George I

For seventeen months Queen Elizabeth II used the Great Seal of her father King George VI. Her Seal was designed by Gilbert Ledward RA and engraved by the Royal Mint. It is six inches in diameter and weighs 135 ounces. On the obverse the Queen is shown mounted on a horse in the uniform of Colonel-in-Chief of the Grenadier Guards.