It seems likely it is a memento mori, a reflection on remembering death. Wikipedia says: 

“The concept of “remembering death” is expressed throughout ancient Greek and Roman philosophy. In Plato’s Phaedo, Socrates states that the sole purpose of practicing philosophy “is to practice for dying and death.” Rather than being a morbid directive, the statement espouses mastering one’s fear of death by recognizing the body’s mortal reality and pursuing knowledge, which nurtures the immortal soul”. 

 So our assumption is that the scene depicted is likely to be an angel protecting, or perhaps opening the container to allow the skull to be seen  and reflecting that they have finally achieved immortality.   

The chapel was dedicated to St Leger by the monks of Ramsay Abbey in 1426, the old wooden bridge having been rebuilt in stone the previous year.

It once had pub in it called “Little Hell”

It was a bullock market held in the Broadway.

The following locations took part in Heritage Open Day 2023:

Holt Island Nature Reserve
All Saints Church
The Methodist Church
The Norris Museum
Fellmonger House Garden
The Prayer & Education Centre
The Bridge Chapel
The Masonic Hall
The Free Church
The Town Hall
Faizane E Madina Jamia Masjid Mosque
Sacred Heart Church