On the first night of Me and My Girl, director Daniel Evans was forced to explain that Lucas had been ordered to rest his throat on doctors’ orders - and that his understudy Ryan Pidgen would be playing the part of Bill Snibson with just a few hours’ notice.
In such dramatic circumstances, Pidgen was not merely understudy but underdog too - and cast and audience cheered on his superlative performance bringing the entire House to its feet before the night was through. Critics universally applauded him. Tickets are like gold dust.
But the role of Cockney Jack-of-all-trades who suddenly finds himself heir to a huge estate always had Lucas’ name on it. A revised book by Stephen Fry honed the humour, rejoicing in the parallels with My Fair Lady.
And Lucas grabs every comic nuance and drives a belly laugh from it - melding dialogue, facial expression and physical comedy in one. It could not be better epitomized than in a scene in which he is already assuming his new noble status and preparing for his first speech in the House of Lords.
Whether it is to protect his throat or merely the contrast against four extraordinarily powerful female actors on stage is not clear, but the Lucas interpretation does not always have the vocal force that some might expect of this rudely extravagant lead role.
The women led by the outstanding Caroline Quentin and Alex Young - who has developed an even more elegant confidence since the first night - brought real fizz to the evening.
Meanwhile Lucas proves why he is comedy gold - and the wisdom of reviving a musical that avoided an overly slushy story line. This has all the Lucas magical mirth that you would expect heightened by some neat ad libbing, not least a reference to the conductor’s head bobbing above the stage line.
As for Pidgen - who has reverted to more modest appearances in the production - this must be regarded as his biggest break. Mr Evans would do well to find him his own leading vehicle in the 2019 line-up if he can be persuaded to return.