Just to help those in a similar situation to myself...
This can be caused when a dependent library has accidentally bundled an old version of slf4j. In my case, it was tika-0.8. See https://issues.apache.org/jira/browse/TIKA-556
The workaround is exclude the component and then manually depends on the correct, or patched version.
EG.
<dependency>
<groupId>org.apache.tika</groupId>
<artifactId>tika-parsers</artifactId>
<version>0.8</version>
<exclusions>
<exclusion>
<!-- NOTE: Version 4.2 has bundled slf4j -->
<groupId>edu.ucar</groupId>
<artifactId>netcdf</artifactId>
</exclusion>
</exclusions>
</dependency>
<dependency>
<!-- Patched version 4.2-min does not bundle slf4j -->
<groupId>edu.ucar</groupId>
<artifactId>netcdf</artifactId>
<version>4.2-min</version>
</dependency>