Were British spies really wankers?

The Telegraph reports that:

'British intelligence services experimented with using semen as an invisible ink to write top-secret letters, it has been disclosed.

A diary entry belonging to a senior member of the Secret Intelligence Service (MI6) has revealed that during the First World War it was discovered that the bodily fluid could act as an effective invisible ink. '

Interesting but the two bits that really caught my eye were these, first this:

'Furthermore it had the advantage of being readily available. '

Readily? Well not immediately and certainly not inexhaustibly!

and second this:

'at least one agent had to be reminded to use only fresh supplies of the 'ink' when correspondents began noticing an unusual smell. '

Words fail me...