The regiment's display is an impressive sight

The shock waves from the 100-year-old field guns dislodged a two-foot square section of ceiling at the Farmers' Union of Wales pavilion during a six-gun salute.

The incident happened at the end of the King's Troop Royal Horse Artillery's twice daily display.

No-one was injured by the falling plaster.

Now the regiment, fresh from France's Bastille Day parade last week, have agreed to a retreat.

The 13 pound guns are being moved back 15 metres to reduce the shock waves from the blasts.

The guns are at the far end of the show ring, opposite the FUW's building, when they are fired.

The whole place just shook and it's amazing the whole of the ceiling didn't come down Mair Ashton Jones, FUW receptionist

FUW show receptionist, Mair Ashton Jones, who witnessed the incident on Monday, said: "The whole place just shook and it's amazing the whole of the ceiling didn't come down.

Shock waves

The field guns 'shook' the building

"Those of us who have been at the show for a few years are used to the guns, but they seem louder this year.

"I'm not sure how the noise affects the animals."

Union spokesman Alan Morris added: "We had a word with the troop after their display and they came round to see if we were OK.

"The troop subsequently agreed to move the field guns back 15 metres to help reduce the shock waves.

"Everybody is very impressed with the troop's display and it's clear that it's a real crowd pleaser, but we didn't expect our ceiling to collapse because of it."

Captain Nick Parker of the King's Troop, from the show in Llanelwedd, said: "We fire these guns all round the country and we've never had this problem before.

"There may have already been a crack in the ceiling prior to the firing of our guns.