Unknown weed plant at sand dunes

Unknown weed plant at sand dunes

Observation - Unknown weed plant at sand dunes - UK and Ireland. Description: Tall weed type plant with pink cluster of thin petals at the top. Stem lined with pairs of ovate pointy leaves. Looks similar to variations of Knapweed, but not confident of this.

Tall weed type plant with pink cluster of thin petals at the top. Stem lined with pairs of ovate pointy leaves. Looks similar to variations of Knapweed, but not confident of this.