Commercial analysis: Section 1(3) of the Law of Property (Miscellaneous Provisions) Act 1989 (LP(MP)A 1989) provides (among other things) that ‘An instrument is validly executed as a deed by an individual if, and only if—(a) it is signed, (i) by him in the presence of a witness who attests the signature…’. A loan was offered by the claimant lender to Rhombus LLP. A guarantee (the ‘Guarantee’) of Rhombus LLP’s indebtedness, purporting to be a deed, was signed by each of the three defendants, and signed by a single person purporting to be a witness, before being returned to the claimant. The defendants later denied that that the Guarantee had been validly witnessed or attested because of the physical and temporal circumstances in which it was signed. His Honour Judge (HHJ) Tindal examined the law on attestation and found that LP(MP)A 1989, s 1(3) had been complied with; before further finding that, in any event, the defendants would be estopped from denying that the Guarantee was a valid deed. Written by Tom Nixon, barrister at Quadrant Chambers.