Toaru Majutsu no Index Light Novel Volume 17

Chapters

 * Chapter 1: 何気ないやり取りの違和 Irregular_Spark.
 * Chapter 2: 雲の上に浮かぶ鋼の戦場 Sky_Bus_365.
 * Chapter 3: イギリス迷路の魔術結社 N∴L∴
 * Chapter 4: その剣は戦と災厄を招く Sword_of_Mercy.
 * Epilogue: それぞれの思惑と胸の内 War_in_Britain.

Summary
Euro tunnel which connects England and France gets bombed. England is having hard time getting import goods thanks to tunnel shutting down as a result. Tsuchimikado asks Touma to go to Britain as Index's guardian, because there seems to be some sort of magic organization at work here, and they need Index's help. Before Touma could say anything sleeping gas grenade is thrown in from next door.

When Touma comes to he's already at the airport. Tsuchimikado got a ride ready for him (monster airplane they used to get back from Italy), but Touma and Index decides to use a regular airplane instead, leaving their cat to travel by himself on the super airplane. (which Itsuwa came to pick up) They use inter connective flight headed to Scotland and than to London since direct flights were sold out. During the ride the airplane is about to be hijacked by French extremist who claims tunnel bombing is England's act to try and cut ties with France. Necessarius tries to use magic to interfere the hijack but is interrupted by unknown source from Scotland. Index gets attacked by him and Touma gets pissed, corners the guy and beat the crap out of him along with the other guy.

Once they're there, Kanzaki picks them up via helicopter and heads straight to Buckingham Palace. It turns out the queen herself was the one who called Index. There he's introduced to the royal family and gets a lecture on Curtana carried by the queen. It's a sword that grants power of an angel to royalty, but the original has been lost for centuries and what the queen was carrying is a copy of original. After the talk they send Index to investigate the tunnel with the knights and princesses. Touma is asked to stay out of it because they don't want him to break anything. They also find out that the group called New Light was the one who interrupted Necessarius's spell and they're headed to London with some kind of luggage. New Light interfered because if the spell wasn't interrupted, the plane would've landed on the road connecting London and Scotland, which would've delayed their travel. Touma tags along Oriana to help her capture the New Light.

Lessar from New Light makes a mistake and gets tracked down. She is spotted by Touma and Oriana while on the run. They fight but she manages to get away and they continue the chase. Itsuwa and Kanzaki manages to capture two of the New Light. The suitcases New Light was carrying allows one to send its contents from one suitcase to another in an instant. When Touma and Oriana corners Lessa, she says that New Light was only here as means of transportation and sends the contents of her suitcase to their client. She gets shot to be silenced right after, but Touma manages to pull Lessar away in time to save her life. Oriana recognizes the weapon used to attack Lessar. It was a weapon used by the knights of England.

New Light was carrying the original Curtana recently excavated, and their mission was to bring it to 2nd princess Carissa. Carissa starts a coup right after Index confirmed that the French magic was behind euro tunnel bombing and takes her custody. She orders the knights to take over all the major facilities throughout England. Battle between knights and mages erupts all over, but with the Carissa's blessing knights subdue most of the Necessarius. Necessarius drops the fight because they're outnumbered to begin with, and goes into hiding. Carissa's reason for coup was that if the war between Academy City and Roman Catholics did happen England will be either wiped out by Romans or become Academy City's puppet. England need to act now if it was to avoid that and become its own nation as well as the head figure of Europe. Her next move was to kill rest of the royalty so that no one else can use the Curtana. She chases after one of her sisters, Villian, who managed to get away during the confusion. Kanzaki tries stop them but she's taken down by Knight Leader. Carissa catches up and gives order to Knight Leader to kill Villian, but Aqua comes in and saves the day.

The queen and Archbishop was captured by knight but managed to get away. Touma and Oriana splits, Oriana staying to help out Sherry who's fighting against the knights, and Touma has to look for someone to cure Lessar. He makes it to the Necessarius girl's dorm and leaves Lessar under Orsola's care. Now he has to help nuns get away from knights and go rescue Index, volume ends.

credit: bob4000 and Lummie from AS