They can provide lightning-fast revenue gains but can also very easily be blown off track.

Accelerated bookbuild activity - where a bank takes a block of shares and quickly sells it into the market with little or no marketing - is weeks away from hitting an all-time high in Europe. There has been $105.7 billion of activity in the year to December 2, according to Dealogic, close to beating 2013's full-year figure of $112.5 billion.