L is for... Liz 10

The Doctor encountered Liz 10 on the generational space vessel Starship UK. It was the 33rd Century, and the Earth had been ravaged by solar flares. Each country built its own space ark and set off for a new home. This was the vessel carrying the populations of the United Kingdom, as well as some of its historic buildings. Liz lived in Buckingham Palace, as her full title was Queen Elizabeth Xth. She liked to mix secretly with her people, when she wore a porcelain mask. She was convinced that her government was keeping a great secret from her, and so approached the Doctor for his help in discovering what it was. He had discovered that the vessel lacked any engines, yet still moved through space.

He also realised that Liz's mask was centuries old, yet designed to perfectly fit her features. She was much older than even she realised. When she confronted her Prime Minister, Hawthorne, at the Tower of London, she discovered the truth.

Starship UK relied on a captive giant space whale to propel it through the cosmos. The creature was tortured to make it move. The UK population were to be informed of this and could vote to release it - at the cost of the vessel's likely destruction. Alternatively, they could vote to forget all knowledge of this and travel on oblivious to the creature's well-being. Liz herself had set this up and had voted to forget over the decades.

When the creature was freed by the Doctor, it transpired that it was willing to help anyway.

Sometime later, Starship UK was visited by River Song who had come looking for a painting in the Royal Collection - an image of an exploding TARDIS, which was the work of Vincent Van Gogh. She needed this to warn the Doctor. Liz stopped her - but agreed to her taking the painting after seeing its subject.

Played by: Sophie Okonedo. Appearances: The Beast Below, The Pandorica Opens (2010).

• In 2003, Okonedo had played the companion Alison in the animated Doctor Who adventure Scream of the Shalka. She would have continued with the role had this gone to series, but it was cancelled after the announcement that the TV series would return in 2005.