Renegades - Shaun Hutson

Immortality - the ultimate secret. David and Laura Callahan, like others before them throughout the ages, will stop at nothing in their perverted quest for it. But for Callahan, a multi-millionarie gun-runnner, eternal life has never looked less likely: he is being hunted both by a renegage gropu of hired killers and by two British counter-terrorists. And nobody knows who hired the killers - or why...
In a race against time, a trail of violence and terror leads from a desecrated church in France to London and on to strife torn Ireland where modern terrorism battles against ancient powers and a terrible secret is revealed. A long forgotten secret that will threaten the lives and souls of those involved. And when the final confrontation comes, the living will envy the dead.