BoE: The move in gilt yields last week threatened to exceed the size of the cushion for many LDI funds.

They go on to say..

Had BoE not intervened, a large number of pooled LDI funds would have been left with negative net asset value and would have faced shortfalls in the collateral posted to banking counterparties.

This is basically an exercise by the BoE in making it clear that they singlehandedly saved the Gilt market - Some may beg to differ and side with 'it was a storm in a tea cup'

BOE's Cunliffe: Closely monitoring LDI funds to ensure resilience

BoE says it will unwind gilt market intervention once risks have subsided