The Knights Templar were the builders of the church, and they were certainly a poweful bunch. So powerful, in medieval times, that the Master of the Temple was entitled to sit in parliament as primus baro (first baron).
Their influence was temporary, though, with Edward II taking control of the church in 1307, and gifting the site to the Knights Hospitaller, who rented the Temple to two colleges of lawyers, who are still basically there today.
The church, like so much of London, was affected by the Second World War bombings, and was renovated by the architect Walter Godfrey. The renovation included many Wren originals, which were discovered in storage and used as part of the new church.
It was also in The Da Vinci Code, but your author finds this to be tedious. For more information opn the chuch in general, visit http://www.templechurch.com