No, Lucas Herbert's caddie did not break a golf rule at The Open

Australia's Lucas Herbert stormed to the top of the leaderboard on day two of The Open. 

The LIV Golf recruit rolled in six birdie putts on Royal Birkdale's front nine to make the turn in a remarkable 28 strokes. 

It saw him equal Denis Duirnan's front-nine score set in 1983, also on the Southport links. 

Two more birdies followed at 11 and 12 to hand the 30-year-old a precious two-shot lead.

With two more par-fives remaining, viewers of golf's oldest major were questioning whether or not Herbert would break the course record, set by Branden Grace here nine years ago. 

But all of a sudden the attention was not on Herbert's stunning golf but rather the actions of his caddie Nick Pugh. 

TV footage on Sky Sports showed Pugh pulling out a rangefinder on the 14th tee box. 

Herbert smashed his drive into the fairway bunker and Pugh likely wanted to check and see if his golf ball was plugged.

The commentary team were quick to point out that distance measuring devices are not allowed and their usage will result in a two-shot penalty under Rule 4.3. 

But it was then it was clarified minutes later that the R&A ensures that, during competition days, there are no batteries inside the chamber.

Therefore, Pugh was using the device - as first suspected - as a pair of binoculars. 

"To give you an update, the R&A ensures that batteries are removed so they can only be used as a binocular thing rather than a measuring device," said former tour pro turned analyst and pundit Andrew Coltart. 

Still, it was a strange decision for Pugh to make - given the optics of the situation. 

The news will come as a relief as it would've been a horrid way to disrupt his round. 

We'll wait and see what Herbert has to say about the situation when he gets off the course.

You can follow all of the action from day two of The Open with our live blog. 

More to come.