Which event will revoke Niall's Will?

The event that revokes a Will is typically associated with changes in personal circumstances that impact the validity or intentions expressed in the original document. In many jurisdictions, marrying generally leads to the revocation of a Will made prior to the marriage unless the Will was specifically made in contemplation of that marriage. This is established to ensure that the new spouse is considered in the distribution of assets.

When Niall gets married, the legal implications surrounding his estate planning change significantly, which directly triggers automatic revocation of any prior Will. While making a new Will will also revoke the previous one, it is more of a deliberate action rather than an automatic event like marriage.

Changes in domicile alone do not invalidate a Will; instead, they might require the Will to be re-examined or updated depending on the laws of the new location. Thus, while making a new Will (which is a proactive choice) is one way to revoke a previous document, it does not stand on the same grounds as marriage, which automatically revokes the Will. Similarly, changing domicile does not inherently affect the validity of a Will.

Therefore, the event of marrying is the clearest and most definitive action that results in the revocation of Niall's Will.