"Legal experts say Roberts hopes to follow the example set by his late mentor Chief Justice William Rehnquist at then-President Clinton's 1999 trial."

"Rehnquist, for whom Roberts clerked in the 1980s, once mused that during Clinton’s proceeding he 'did nothing in particular, and did it very well,' lifting a line from Gilbert and Sullivan. Eric Claeys, a law professor at George Mason University and former Rehnquist clerk, said Rehnquist’s approach was framed by the 1986 rules. The rules say the presiding officer 'may rule' on all questions of evidence, like instances where the relevance and significance of a document or witness testimony is unclear. However, a single senator can appeal the ruling, triggering a Senate vote, where some say Roberts would break a 50-50 tie, though that is disputed. The presiding officer also has the option to stay mum on an evidentiary question and send it directly to the Senate for an up-or-down vote. Rehnquist generally avoided this option during Clinton’s 1999 impeachment trial, Claeys said. Instead, Rehnquist applied the relevant precedents, then left it up to senators to decide whether to reverse his decision. 'I don’t think that Chief Justice Roberts will play a bigger role in President Trump’s impeachment trial than Chief Justice Rehnquist did in President Clinton’s,' Claeys said. 'I expect Roberts will follow the same strategy.' However, some legal experts believe today’s more intensely partisan atmosphere may force Roberts to depart from the course charted by his predecessor...."

From "Trump impeachment trial drags Roberts into spotlight" by John Kruzel (in The Hill).

The Gilbert and Sullivan song is "When Britain really ruled the waves" (from "Iolanthe"):

When Wellington thrashed Bonaparte,
As every child can tell,
The House of Peers, throughout the war,
Did nothing in particular,
And did it very well:
Yet Britain set the world ablaze
In good King George’s glorious days!